Trump knew he had a very short time to break everything and he did. Because he knew it takes much longer to fix things. However he was the one who did it.
Trump was a true rule-breaker who did manage to do quite a lot in the international arena, where he had far greater leeway to make changes beyond congressional control. Much of that activity was destructive, because Trump proved quite adept at smashing things. Indeed, Trump smashed things—the Iran nuclear deal, détente with Cuba—not just because of a peevish desire to destroy his predecessor’s legacy but as part of a scorched-earth policy to FUBAR the federal government for generations to come. As a result, Biden will spend much of his term picking up the pieces—and that’s a whole lot harder when you’re in handcuffs.