He failed to file the paperwork disclosing he owned more than 5% of Twitter until 11 days after crossing the 5% threshold. That is there to allow the public to know that someone is buying large amounts of stock so the public won't sell at artificially low prices. Because Musk didn't disclose the SEC suggests he saved at least 150 million dollars byrublic, ON TWITTER, during the deal. That he had violated SEC rules buy not disclosing he owned more than 5% already and as such should not be allowed to buy Twitter.
I'm sure it was just an innocent mistake from Mr efficiency