Biden isn't a stunning speaker, but here's the thing: beneath that is an intelligent, competent politician, even if he occasionally makes mistakes or doesn't translate words into action. If he doesn't have all the answers, he admits it and delegates tasks to people who are better-suited.
With Trump, the surface (which isn't that great to start with) is all he has. His ideas and governance were at best incompetent, were tied to ego and ideology rather than evidence. Many of them are intentional, malicious lies. And at worst... well, they may well have led to hundreds of thousands of avoidable deaths.
I'd much, much rather have an awkward public speaker with sound (if unspectacular) political actions than a skilled orator who delivers bad ideas with sugar on top.