I don't think "but things were looking up for him so he wouldn't have committed suicide now" necessarily holds water. People commit suicide for reasons inside, not outside.

It could be that, after the rush of the acquittal, he started to think about how it didn't make any difference. He's still in jail, and as much as his lawyer talks about the appeal having a good chance, if he were guilty he'd have to know that the evidence against him was still there. After being in jail for four years, depression was a pretty likely companion. It may have hit him all at once what he'd had, and what he'd thrown away.