Steam has released its hardware and software survey for April 2020. Taking a look at the chart for PC video card usage by % change this month clearly shows that it's not just sales or new releases affecting positions. AMD has two products in the top four movers alone, with the Radeon R7 M445 and Radeon RX 5700 XT gaining strong % changes.
https://www.notebookcheck.net/AMD-disrupts-Nvidia-stranglehold-in-Steam-s-April-hardware-survey-thanks-to-an-uptake-for-the-Radeon-RX-5700-XT-and-an-appearance-by-the-Radeon-R7-M445-laptop-GPU.464252.0.html