According to his recent interview on Primeagen, he argues that WPEngine operations incur high costs to his company, due to the millions of installations consuming resources from Wordpress.org. And despite being a very large player, they contribute nothing back to the ecosystem. He argues that they even illegally modified code attributions (stripe plugin) which diverts millions from Automattic. The fact that it took, apparently, so long for him to take some action can be interpreted in his favor, because he tolerated a lot along the years. Add the fact that they had somewhat good relations before WPEngine being taken over by private equity. So this is not about trademark, trademark is the best weapon he has to fight back against a very bad neighbor. And being the sole trademark holder, Automattic can enforce it arbitrarily, as it sees fit. Taking side with WPEngine I think is not only rationally baseless, but also immoral, since they put nothing and only take, which is in the very opposite of what Matt represents, whether or not you like Wordpress.