To use your own logic, if the founder of a FOSS project leader wants to have a conflict of interest (which is a negatively biased framing of them earning a living off their two decades of hard work), they’re allowed to. If they want to criticize someone else making money off that project, they’re allowed to. It is downright bizarre that you think it is acceptable that “Satan” can profit off Wordpress but with the creator of Wordpress you suddenly take issue with a “conflict of interest”.
To further use your own logic: Is Matt violating the GPLv2? No. OK, then why are you whining about him? He has the same freedoms that you ascribe to WP Engine or others. It just looks like you’re carrying water for an evil private equity firm with a long track record of being evil. All to attack someone who actually created a massive positive impact on the world. Yea no thanks - no one is convinced by this weird demand that Matt needs to step down.