My guess is that it wasn't really a conspiracy but that most distro developers do not give a rats ass about good desktop experience, thus they simply package whatever those who do work on desktop stuff and get done with it. "Those who work on desktop stuff" are basically Canonical and Red Hat and both of them decided, for various reasons to stick with GNOME, partly because GNOME at some point (2.x days) was a good enough desktop and partly because everyone had settled on Gtk+ as the defacto Linux toolkit (itself mainly thanks to it being usable from C, written in a way that allowed other languages to interface with it almost automatically and of course having a license usable by everyone from the beginning) and GNOME was the defacto desktop environment for Gtk.
Of course all that was on the Gtk2/Gnome2 days and Gtk3/Gnome3 broke a lot of bridges, still the complexity of the desktop and the fact that GNOME has actual paid people working on it ended up with the project having a lot of inertia and they are the projects that do most of the work no matter how misguided that work might be.
After all, those who do the work are those who decide how that work will look like. Anyone else, regardless of them being right, wrong, having better or worse opinion on that work, is irrelevant.
If you want to take control of the Linux desktop away from GNOME you need to replace the GNOME stack - not just the desktop, but also the toolkit, the inter-application communication, sound libraries, etc - with something that is objectively better (for a definition of better that a majority agrees with it) and convince other developers to use it.