The thing with Maxar, etc, is the question: what happens if SpaceX just decides to add an extra Earth-facing sensor bay to every single new Starlink sat?

Because the next step for SpaceX would be to start putting hardware that directly undercuts Maxar and others into those bays. Anyone who's doing smallsats should be extremely concerned by the possibility.

SpaceX is already getting in on that MIC game with Starshield - a series of customizable Starlink-derived sats that SpaceX has reportedly offered to Pentagon at bargain prices. So they clearly are trying to get into new market segments, and they aren't subtle about it.