The Billy Mitchell strategy doesn't make sense in this case though, since I guarantee you that all three named entities have more money to fight lawsuits than Hans Niemann.
We don’t know what Hans’s resources are. Perhaps his lawyers are working pro bono or otherwise agreed to take his case on contingency, with the rationale being that Hans is a public figure and this case may serve as advertisement for the law firm.
Same point applies, since a firm is not gonna take a pro bono (this would actually be contingency fee) case they don't think they can win, which was what the OP was saying.