I dumped them after they fought against competition by selling very limited stocks of the Zero at very low prices, possibly at a loss. They released just enough of them so that someone somewhere could always tell that they were the cheapest board available, but in fact they were pretty much unobtanium everywhere, except of course in "friendly" sites and forums where every post about the shortage was immediately replied with "I could buy one at XYZ...", where xyz inevitably turned out to be a shop with none in stock. This happened much before Covid19 and chips shortage hit the market, in fact competition had cheap alternatives in stock and I could buy some NanoPi and OrangePi, but the RPi had much better press. I'm considering to make an exception for the Pico for being a really interesting product, but my last Linux RPi has been the 4 and I don't plan to go further.
Before the pandemic, I picked them up for $5 regularly at our local friendly computer store. They even had 0w's for $5 as a gimmick (they were supposed to be $10) with purchase limit of 2 or 5 (can't remember). I'd just pick up a couple every time I went to that store. I've got a sandwich bag full of them now.
I think it was very much the supply chain snags of pandemic that made them get weird high prices everywhere.
So your assertion is that Raspberry Pi was using a Zero as a loss leader AND that it was out of stock. And some how this was enough to stifle competing products? And the competing products you've cited all have "Pi" in the name because they only exist to fill the gaps that Raspberry Pi products don't fill. For example the NanoPi is a Zero competitor that differentiates itself by having Ethernet.
Raspberry Pi dominates the market because it was the first to enter it and provides a limited product catalog that has limited churn with comprehensive support and regular software releases. The same cannot be said for it's competition which historically offered horrible software support land quickly iterated on products meaning that support generally only existed for the very latest.
I know it's an anecdote, but I found out about them bundling the Zero with a Raspberry Pi magazine here in the UK few days after it launched, and I was able to pop down to my local tesco and grab a copy(and it wasn't the last one either). Since then I bought a dozen more for various projects around the house and it's never been a problem, Pimoroni or the Pi Hut always have some.
