From Reddit discussions, if they can be trusted, there is nobody who can remove Matt from any position. It's a private company and the investors were given non-voting shares.
Even "taking their part of the money out" is not guaranteed. Again, it's a privately traded company, so there's no open market. You have to find someone willing to buy your shares from you and make a deal with them.
but the opposite is true too: don't take money from investors unless they let you keep control of your company. for every case like this there are probably a dozen cases where investors took control of a company and ruined it for the sake of making money.
Presumably if you as a founder are not driven by a desire to make money and your investors are, you 100% should be ousted. This is the principal-agent problem at work.
My understanding is that the investors signed proxy voting rights over to Matt. They are mostly ordinary shares, and may be revocable. [1]
[1] https://ma.tt/2021/08/funding-buyback-hiring/