They did though by patterning with publishers. Forcing physical releases to go through Steam as DRM. Killing the physical pc gaming market.

Not only does this not describe forced retail exclusivity, it's three different statements that are all false in their own ways. Distribution agreements aren't exclusivity agreements, Steam only deals in digital copies not physical copies, DRM implementation is optional, and there are no stipulations barring publishers from making or distributing physical copies.

We've gone from one incorrect statement about Steam to five.

They also have their Non-Favoured-Nations clause, meaning a game can’t be sold for cheaper off Steam.

You mean the Most-Favoured Nations clause that five people filed a suit over, based on a a Tim Sweeney tweet from 2019? Not only was that suit silly, it doesn't even make sense as this sort of clause is extremely common in retail and not at all unique to Steam or Valve compared to other storefronts.

Only as they geared up to sell their own consoles.

You also don’t seem to be fully aware of Valve’s contributions to Linux gaming.