Myself, I’d rather see someone like Shoeless Joe Jackson get reconsidered first before we address players who admitted breaking the rules. He was acquitted in a court of law and set several offensive records in the 1919 World Series but commissioner Landis banned him anyway despite a lack of evidence.
Jackson admitted to participating in the conspiracy and taking the money in oral testimony before a grand jury. He later denied he ever said those words (plainly perjuring himself, as the court in which he made those denials called the stenographer who took the grand jury testimony in the first place as a witness), and spent the rest of his life spinning the fiction that he somehow wasn't involved (indeed, his stories kept getting less and less plausible as he added details that contradicted his previous statements)
Jackson always claimed that he didn't actively throw any games, but given how blatantly he lied to a court in a lawsuit he initiated (earning himself a warrant for perjury, which was ultimately never enforced, presumably because Jackson never went back to Wisconsin, where the warrant was valid), I'm not inclined to take his statements on the subject at face value.
Because we can't prove one way or the other whether Jackson actually was intentionally playing below his abilities, we can only infer it, and there are plenty of indications that Jackson was actively trying to lose in the games that were fixed (essentially Games 1 through 5), as he underperformed in those games.
His acquittal (along with the other seven Black Sox) in the 1920 criminal trial appears to have been a case of prosecutorial failure and jury nullification, rather than an honest assessment of his guilt, given that
he had already admitted his culpability, both to a grand jury and to reporters after giving the testimony. He only reneged his testimony because he had apparently believed that he had been granted immunity in exchange for testimony, which was not true (Jackson, Cicotte, and Williams all testified), and suddenly facing criminal charges, tried to deny he had said what he had said (the court had none of it).
It's unlikely that Jackson's testimony was false or planted, because Jackson was the one who supplied various details (ultimately corroborated by others) that were unknown by investigators in the first place.
Basically, there is a ton of evidence Jackson was guilty. He did it.