They chose an arbitrary cut-off date for hardware support for their new OS. They decided not to support old stuff anymore and they had to pick a date/technology platform. It was always going to be arbitrary. In my opinion they should've picked a clearer distinction (i.e. require a certain level of AVX support so all binaries can be built with AVX optimizations enabled) but I can see why they chose to do this. After all, they're going to have to support the OS for ten years, that four year old CPU is fourteen years old by the time Windows 11 goes out of support.