The question is more "why would the President self-immolate themselves politically for someone who appears to have minimal actual political capital, especially now that they're broke?"
Presidents generally don't suffer much from pardoning the wrong person.
There's maybe one President that didn't get elected because of his use of the pardon. But then, Ford wasn't elected President or Vice President before he pardoned Nixon either.
Otherwise, I'm not aware of a pardon so controversial that it became a major campaign issue. And for a second term President, there's not really any downside.
Because the pattern they usually follow is to pardon the questionable cases (personal friends, people with financial ties to the President, etc.) just before they go out of office.
