Tudors: Why was Richard III able to usurp the throne in 1483?

There were several reasons why Richard III was able to usurp the throne from young Edward V. His potential political opponents were very weak; the family of Woodvilles had very little power and the arrest of Earl Rivers killed any chance at controlling Edward V - they were ultimately too slow to act. Equally, the violence and speed of Richard's actions mid-June 1483, such as the arrest and execution of Hastings and imprisonment of other opponents, took advantage of the Woodvilles' delay in action and there was no time to organise opposition. Richard had great support from significant noblemen such as Hastings, Buckingham, Howard, and support from his northern army helped to alarm and intimidate opponents further. Richard used the element of surprise to his advantage, as up until Hastings's arrest he had stressed his loyalty to Edward V, and never showed signs of wanting greater power. Equally, his loyalty to Edward IV was consistent since 1471. It is also true that uncertainty and confusion of what was really happening played into Richard's hands - in addition, the public had bad memories of the minority rule under Henry VI, which they did not want to happen again. What sealed his usurpation was the proclamation that Edward IV's children were illegitimate, which made several potential opponents hesitate in any action against him.