However, I think that this speaks more to the degree to which Apple have put the torch to Mac gaming than it does to the size of Linux gaming.
Perhaps the key is for them to work closely with Valve to make Proton work well on macOS, which would also neatly deal with the 32-bit issue because WINE/CrossOver on macOS handles 32-bit Windows binaries just fine despite macOS having dropped support for 32-bit Mac binaries ages ago.
This however seems unlikely because even setting aside the issue of how Apple might see doing this as pushing users to a competing marketplace, it also cedes some amount of the Mac's functionality and thus marketability to a third party which Apple has never been keen on.
Apple are doing something very similar already with their Game Porting Kit framework. It supports DX12 games translated to Metal and runs very well. This effort only become public this year, though, so the fruits of that labour are yet to be borne.
But then again, let's face the truth: Apple doesn't care about having Counter Strike on your Macbook. They make billions doing absolutely fuck all and taking 30% of all microtransactions on all App Store games.
The only real impediment is that they need to care. The one thing in common across all successful gaming platforms is that the platform owner cares a lot and works closely with game devs to make things work:
- Microsoft/Nvidia/AMD ship game-specific patches and optimizations for Windows games
- console makers work closely with third-party devs and give advice, feedback, certification, etc.
- Valve specifically has put tons of effort into SteamOS and certifies individual games as ready/not ready for the Steam Deck
All it takes is a platform owner who cares, and cares on the level of interventions for particular games, but this is totally foreign to Apple's DNA (both in general, and for games in particular). They'd need a huge culture shift.