Nobody invited him - he just showed up and plunked himself down, reeking of insecurity and desperation but acting like he doesn't know that everyone hates him.
Elon: Then I perform a hostile takeover of the game master role of this campaign. I am now the GM.
Snatches notes from the GM
GM: What the fuck?! Give those back!
Elon: Shut up Greg! Look at all this shit! You know what, I don't like this. I'm scraping this fantasy campaign as of right now. This will now be a dystopian science fiction campaign with heroic space Nazis fighting evil trans communists.
Group: Damn it Elon! Not again!
Elon: And we need an investigation into how the previous GM was running this. Too much nerdy woke shit! Timmy, you seem loyal to me. You are now in charge of the Department of Dungeoneering Efficiency! I want you to go through Greg's room and take so his GM stuff.