That's very nice to hear.
But diffuclt to beat valve here, they are actively contributing to drivers and wine. When you buy even just windows software from steam you are helping funding that.
I see no simpler explanation why someone would buy out a subsidiary like that.
All in all, GoG thrives on people being sentimental and it's totally in character for the owner to be sentimental as well.
Same with anti-cheat really. The most common reason I hear people don't make the switch to Linux is that certain games work only on Windows due to the type of anti-cheat they use.