Both Macbeth and King Lear seem to impose their problems and suffering gratuitously upon themselves. Macbeth murders Duncan and manages to pin the crime on Malcolm and Donalbain after they flee for their lives. Once he is King of Scotland, Macbeth is not satisfied with what he has achieved. He commits further crimes and becomes a terrible tyrant. People flee the land. Chaos ensues. The English monarch raises an army to invade Scotland, and Macbeth is killed in a duel with Macduff. Malcolm probably could not have received the military assistance of the English king just on his own merits and his claim to be the rightful Scottish monarch.
King Lear is so proud and inflexible that he will not consent to his daughters' terms. He could live in luxury with both of them alternately and be treated with respect and courtesy if he relinquishes his one hundred knights. Instead, he insists on living outdoors. Macbeth's problem is not that he murdered Duncan, but rather that he elected, unnecessarily it would seem, to become more and more tyrannical until he turned everyone in Scotland and England against him.