Originally Posted by
mangosta71
Robert was willing to forgive anyone except a Targaryen. I suspect that his refusal to forgive them stems from his belief that Rhaegar kidnapped and raped his fiance. (We don't know if their relationship was consensual or not and we probably never will, but what matters is that Robert believed that Lyanna was forced.)
Robert Baratheon was the Ulysses S Grant of Westeros. He didn't want the responsibility of power - he just wanted the booze and whores that came with the power.