AMD actually does well in the retail market. Don't let Steam surveys and mobile, which is 80% of all PC sales, distort things. When polled, 1 in 3 DIYers are using an AMD GPU. Last Q AMD cited increased Radeon sales for helping prop up numbers. We are a very different market and that's the one MSI is leaving. AMD AIBs make better margins than with Nvidia from what I have read. See EVGA for reference.
My hypothesis is - MSI is bailing on AMD GPUs because they have such a small slice of the pie there. PowerColor, Sapphire, and XFX are the big 3. As I knew some would only buy EVGA for green, I know others that only buy Sapphire or PowerColor for red. XFX has really stepped it up though with RDNA 2&3. Both XFX and ASRock seem like they are gaining momentum. The Acer cards look well built, looking forward to seeing them in reviews. Meanwhile MSI RDNA 2 are the ugliest cards. And the younger crowd are obsessed with showcase PC builds, of late the fish tank designs. I rarely see them in the battlestation builds. I suspect most of their cards go in their own prebuilts.
This is all my speculation of course, so pinch of salt and all that.