My recollection is that the accusations of Lula being implicated in the Lava Jato wasn't substantiated, but the accusation was used politically to send him to jail and thus prevent him from running for office against Bolsonaro. In the end all of the major charges against Lula were annulled [1], and the charge that got him sent to jail (bribery based on property being given to him, where no record of any sale or transfer of ownership was ever produced) was a political character assassination job and frame placed on him by a different judge in coordination with political opposition working to prevent him from running in the 2018 election[2].
[1] https://www.bbc.com/news/world-latin-america-56326389
[2] https://www.ohchr.org/en/press-releases/2022/04/brazil-crimi...