Well, you may well ask. King Stephen (1135-54) was a good bloke but a rubbish king. To paraphrase Machiavelli, good blokes make rubbish kings. As he wasn't expected to be king in the first place, we know very little about his early life but we do know, from the portraits we have, that he wasn't much of a looker. His reign is known as one of the darkest periods in English history, or 'the Anarchy'. As the Anglo-Saxon Chronicle tells us:
In the days of this King there was nothing but strife, evil, and robbery, for quickly the great men who were traitors rose against him. When the traitors saw that Stephen was a good-humoured, kindly, and easy-going man who inflicted no punishment, then they committed all manner of horrible crimes... And so it lasted for nineteen years while Stephen was King, till the land was all undone and darkened with such deeds, and men said openly that Christ and his angels slept.
Whenever there's a crap medieval monarch you can be pretty sure there's a succession dispute not far away. Indeed, Stephen shouldn't have really been a contender.
Stephen wasn't even the first choice in his own family - however, his hapless brothers insisted either on being barking mad or dropping dead at inopportune moments. The only surviving and sentient sibling, Theobald, was more interested in his ancestral lands of Blois than in battling for the crown of England and so Stephen had only the offspring of Henry I to contend with - all 29 of them.
Stephen was a grandson of William the Conqueror, and nephew of Henry I. Despite having sired a startling number of children, his only (remaining) legitimate son died in 1120. William of Æthelthing, having been rowed to safety as the White Ship sank, insisted on returning to the wreck upon hearing the cries of his half-sister the Countess of Perche. This was all very noble and that but rubbish for the future of the succession as they both expired.
Henry I then had to decide which of his remaining brood would be the heir. Matilda was the eldest legitimate child and had some pretty impressive political and military alliances - her first husband was the geriatric but powerful Henry V of Germany (the Holy Roman Emperor) but when he popped it, she was (in 1128) betrothed to Angevin King Geoffrey IV. And so, in Christmas 1127, Henry gathered a load of clergy and nobility (including Stephen) in London and got them to take an oath pledging their allegiance to Matilda should Henry die. Henry ended a fairly decent reign with a supreme act of silliness, succumbing to the grim reaper in 1135 after eating a load of lampreys (sort of eel-like things), very much against the advice of his doctors.
A Bit Daft
Henry, perhaps never seeing Stephen as a potential threat to the succession of Matilda, was very fond of his nephew and had given him a load of land in both England and Normandy, and by 1130 he was rolling in it - the richest man in both England and Normandy.
Despite the oath, when Henry died, Stephen and many of the Anglo-Norman nobles were unwilling to accept Matilda as the new monarch. Stephen's brother, Henry of Blois, Bishop of Winchester, had worked hard to gain recognition for his brother's rule from the papacy, but there were other reasons why the nobles were inclined to support Stephen. First of all, Matilda was a girl. Secondly, people thought Stephen might be a bit like Henry I, who was quite good. Additionally, Matilda was married to Geoffrey, a hated Angevin. As well as not being very nice either ('disagreeable, proud, and much disliked') she was out of the country (in Anjou) and for once in his life Stephen took the initiative, crossing the Channel to be crowned king by the Archbishop William of Corbeil on 25 December, 1135. How could it all go wrong? Well to tell you the truth he was a bit of a mug.
The info we have seems to suggest that Stephen was generous and friendly and brave. However, these are qualities more suited to successful celebrity Big Brother contestants than medieval kings. He was hopeless at making political decisions and easily manipulated by those around him. A lot of his decisions were made in an attempt to get people to like him. A bit of forcefulness was required, and Stephen's willingness to give away lands and offices to nobles gave them wealth and independence, rather than loyalty.
Although the first few years of his reign were uneventful, before long the nobility were taking liberties. Some nobles who had supported Matilda, most notably her half-brother, Robert, Earl of Gloucester, remained loyal. By taking no action against errant barons who seized royal castles in different parts of the country, he was virtually encouraging them to strengthen themselves and weaken royal authority. They took property illegally and, in order to stop attacks on the borders with Wales and Scotland, Stephen gave away huge tracts of land to the Scottish king. Similarly, in 1137 Stephen went to Normandy in order to claim the duchy. Unable to capture Normandy, he began losing support and agreed to an unfavourable treaty with Geoffrey of Anjou (Matilda's husband) in order to quell hostilities. In 1139, Bishop Roger of Salisbury and his nephews (Bishop Alex of Lordon and Chancellor Roger), accused of plotting against Stephen and imprisoned on questionable evidence, were arrested and their wealth seized - this outraged the Church. Stephen's jealous tirade against Roger and his fellow officials seriously disrupted the administration of the realm.
Waltz in Matilda
At this point Matilda felt the time was right to step in and assert her hereditary rights. She invaded England in autumn 1139 with her husband Geoffrey of Anjou and half-brother Robert, Earl of Gloucester. They took control of much of the west of England and joined an 1141 rebellion against Stephen which resulted in Stephen's capture (by Robert, Earl of Gloucester) at Lincoln. His government collapsed and, in an unprecedented move, an ecclesiastical Council proclaimed Matilda 'Lady of the English.' Before long she was styling herself as Queen of England, overturning almost everything Stephen had granted or conferred. Before long there was confusion about who owned what.
The profoundly arrogant Matilda thoughtlessly levied heavy taxes and cash demands and was expelled from London before her coronation by enraged citizens. Stephen's forces rallied and captured Robert, exchanging him for the King. Stephen began regaining support, not least from the Church. Though Matilda remained in England until Robert died in 1147, she did not succeed in bringing her husband Geoffrey of Anjou into the dispute (he was reportedly happy that it kept her out of his way).
Stephen was unable to punish Robert and Matilda and the barons began rebelling - not to support Matilda, but to shake off Stephen's authority. Barons were responsible for terrible tortures, famines and some even issued their own currency. Civil disorder and breakdown led to the reign being referred to as 'The Anarchy.' The administration of the English government had collapsed.
Though Matilda had been defeated the succession was still not settled - Stephen wanted his son Eustace to be named heir, and Matilda wanted her son Henry fitzEmpress to succeed to the crown. Civil war continued until Matilda departed for France in 1148. After years of disorder the succession problem was resolved when Stephen's son Eustace died in 1153. Henry came to England to battle for both his own rights and those of his mother. The two sides finally reached a compromise with the Treaty of Wallingford which ruled that Stephen could reign over the kingdom unopposed until his death when the throne would pass to Henry of Anjou.
Stephen died less than a year later in 1154.