It's not at the same scale that AWS and GCP suffocate database vendors, but it rhymes. And it's easy to see why he's mad.
If a very vocal part of the OSS community wasn't so averse to letting small amounts of monopolization happen, we might see open source products that reach significant commercial scale. Where a single vendor or entity can profit and grow big without irrelevant competitors abusing the license to latch onto the product. An open source monopoly could collect good margin and build ambitiously.
It's hard to build a defensible open source business without using fair source licenses, having source available enterprise offerings, or even using an open core design that keeps important parts hidden and out of the commons. That's the only way to defend the magic bits and grow big.
If OSS folks were more tolerant of this, we'd probably see more funding for OSS and extremely viable and defensible open source businesses.
His so-called "democratize publishing" persona is just a complete facade.
Like many sociopaths, he prefers not to draw a clear distinction between actions he's performing for his own benefit and those he's performing on behalf of others, so he often tells a very different story about this. He claims to think, and may actually think, that there's nothing strange or alarming about the open source WordPress project taking sides in a commercial dispute between two vendors.
Indeed, I suspect if you sat down with him in private he'd explain to you that things like the Wordpress Foundation or fiduciary responsibility to Automattic shareholders are legal fictions. In his reality, he's the WordPress guy, and anything which seems to limit or constrain his control of WordPress is just some nonsense he signed off on to keep the suits happy.