The Democratic National Convention hasn’t happened yet, which is where the party selects their candidate. Generally the selected candidate at the DNC is the winner of the individual state primaries. So he could step down and the party simply picks someone else at the convention.
I read in another article that one of Guzman’s sons told him they were flying to look at some property to purchase and then they landed in the US and were immediately arrested. The article gave the impression the son, who was their finance guy iirc, was in on it. What he got out of it I have no idea.