Niemann is pretty much screwed now. Ian Nepomniachtchi asked for extra security after Niemann was a late invite and was pretty much ignored and it doesn't sound like other top players were happy about that. So, as was expected, there are multiple top players that had a problem with Niemann even prior to this tournament. So he is now screwed. If you are running a big money tournament, do you invite Niemann and run the risk of having other top super grandmasters decline?
Playing devil's advocate, but I don't see how he's screwed. If anything I think all this makes Niemann more popular and marketable until there's concrete evidence he cheated against Carlsen in STL (either by Niemann getting routinely beaten by the best players or if there's solid proof of him cheating during over-the-board games).
Also, is it really that hard to set up an over-the-board tournament and not worry about Niemann (or any other players for that matter) cheating? If the other grandmasters are so certain Niemann got to his current status and won certain matches by cheating, I'd think they should be chomping at the bit to play him "on the level" and take him apart. If I'm running a big money tournament, the 1st person I'm inviting is Niemann because he's now the publicity draw because of the actions of other super grandmasters - had they just played him and likely won matches, the Niemann story fizzles on its own if he's not an ascending player.