It may not be his, but that’s all money that could instead be used to convince voters to vote for him. On the flip side, he probably is using that money as efficiently as possible, if he’s found guilty or has to sell a bunch of properties, it may turn off some of his supporters. Thankfully, Biden doesn’t appear to have anything like that hanging over his head(maybe the impeachment inquiry, but it’s appearing to be a nothing burger), so he can focus on convincing people to vote for him.