Why did civil strife break out in England after the end of the Hundred Years War?

After the death of the rightful king in England at that time, an internecine war broke out between Lancaster and York on the one hand against the Plantagenets. This was also the reason that England lost the Hundred Years War, since it was very difficult to fight on two fronts. Ultimately, the civil war or civil strife in England lasted 30 years. At the end of this war, the Tudor dynasty came to power.