From what I've read in the complaint, the reason they're alleging is "no reason," although one claim does list "market manipulation" as a reason with no other facts to support that (which strikes me as something to be stricken as a conclusatory allegation, not a factual allegation, but I'm not a lawyer here).
Especially for something as complicated as security law, I'd expect to see an entire section on market manipulation laying out what the precedent says they need to allege to substantiate their claims and then detailing enough facts (or beliefs to be made good on in discovery) to make that claim credible. Without it, the complaint comes across less as "Robinhood clearly broke the law" and more as "I'm whining because I don't like the contract I signed with Robinhood."
