The reality is likely just market share, hardware and the makeup of that market share.
Macs used to actually be a big gaming platform once upon a time. Myst was a Mac exclusive (built with HyperCard) and Bungie used to make games for macs first before getting bought by Microsoft.
But windows got the upper edge:
1. Much larger slice of the market
2. More of the market is made up of gaming enthusiasts than Macs which are usually either targeting light use, education or professional.
3. You can make affordable gaming PCs with windows. You can’t really do it with any kind of Mac because there’s no product for that market between the Mac Mini and iMac (which were targeted at more casual users) up to the Mac Pro and iMac Pro (which were targeted at professional users)
It’s easier to target the biggest piece of the pie and the one that will buy your products.
That’s why the “API” reason never makes sense, because iOS is THE dominant gaming platform despite having the same APIs as a mac. Game engines often need to support multiple graphics APIs anyway.
So Mac gaming did take off, but it fumbled and never recovered. Part of that is that Apple themselves fumbled as a company, on the verge of bankruptcy before the return of Jobs. What made them successful post his return is also what killed gaming on their platforms: they targeted a different audience.
