So it's collusion when an auto manufacturer stops selling older model cars? It's collusion when you can't buy the 2010 version of tax software?
Microsoft isn't interested in selling you Windows 7, and you can't compel them to. Of course, the offered you (and really, they still do) the free upgrade path to Windows 10 from Windows 7 and Windows 8.x. Consumers aren't being injured, except by their own paranoia.
They don't want older versions installed on new hardware, and they are using their status as a 900lb gorilla to enforce it. As long as they don't prevent Linux, BSD, or other alternative operating systems from running on intel and AMD chips/chipsets, there is no collusion and no injury to consumers. I'm sure it rubs you the wrong way, but then again, if you still won't run Windows 10, it's probably likely anything Microsoft does will rub you the wrong way.