True in that small individual donations are unlikely to fund it. Sponsoring a feature is a thing in open source. Either through a bounty site or a fund me site.
Maybe there just isn't much interest in windows support?
Crystal is a fantastic language for server-side programming where it pairs the performance of Golang with the expressiveness of Ruby.
I imagine most Crystal users love it for exactly that reason and have little interest in development resources being diverted to a platform that they have no use for.