Well they waited an eternity to trade Happ and it cost them. Pearce wasn't a commodity, whether he was traded in June or July, it probably wouldn't have mattered. Toronto Pearce was on the DL more than he was on the field. Couldn't risk that when trying to move him.
Boston Pearce was sprinkled with Alex Cora Magic Dust which turns everything into gold, so his body suddenly was immune to injury post trade. The Jays don't have that magic.