It has been an incredible dynamic few years on the processor front. AMD recaptured processor momentum ever since they released Ryzen processors. I mean just where they are now and where they were four years ago. The effect of their sales was slowly visible in the Steam charts as well.
Now you need to understand that upgrading a PC with a new processor is a rare thing, likely most people do that once every what .. five years? So when you look at all numbers combined, obviously Intel still is by far the biggest. In the past few years, you could see in the Steam hardware survey that Intel was declining and Ryzen on the rise. These are very slow visual to see trend effects in charts.
However, if you look at the latest data, something interesting is happening. Despite all the unfortunate negativity on Intel with the vulnerabilities and price levels and whatnot, they are surprisingly enough regaining that market share on gaming desktop processors.
February 2020 showed AMD had a market share of 21.8 percent, compared to 78.2 percent for Intel. Currently, Intel is on the rise again at 81.25 percent. You can literally see the effect in the chats. It's a surprising development. As it is not really 100% clear what is responsible for the trend and really, it doesn't make much sense either as it is conflicting with (r)etailer numbers bigtime.
I was thinking about it and have one theory though, the sharp decline is happening in the last quarter. Think about this: with the COVID-19 Corona outbreak, everybody is at home, starting up that older Intel-powered PC or laptop again or people are refurbishing an older PC for their kids and people to game on ...
One more chart, here we can see the 2018 October until march videcard spread. AMD is falling here as well, it had roughly 15% market share in 2018 and kept that level for a long time, however currently that is on the decline towards 13.4%