Non-trivial development costs for a niche market. The website has said there's no mac version planned for a year or more. Most games don't bother with mac releases and that trend will only increase now that Apple is firmly decoupling from the PC hardware ecosystem.
If you buy it on Steam, you'd be able to play it through Proton. I assume Proton is available on Macs, but I don't actually know; please check and don't hold me accountable.
Apple did take Wine (well, CrossOver, but that's wine-based), adapted it for Macs, didn't create a merge request for a single line of code, and ended up only advertising the new tool as a demo for how well games run on their hardware to incentivize ports, with no intent of using it as a compatibility layer for players.