Not sure why it would be unexpected? 8.1 was not a good OS from a UI perspective, but it was the last version before Microsoft went all in on making Windows a service and not a product you paid to use.
They still had the incentive to make the OS better and faster. I remember videos from Microsoft at the time showing how fast Windows 8 could get to the desktop compared to 7. They don't really even try to work on stuff like that anymore.