Rimtariro

Don't make it sound like a zero-sum game, because it is not. They don't have to drop any of the support they provide for other languages right now.

In fact, they don't even have to do that much for Swift. They don't have to develop neither the language nor the compiler.

They need to do similar to what The Browser Company did, exposing and allowing usage of their APIs from Swift, and maintain it as their API evolves.

If The Browser Company could afford it, while developing the browser, Google and Microsoft can afford it as well.

It's not about Apple. Google/MS would invest for their own sake, so that it would translate into more apps (earlier, not as a second class citizen) on their platform, which in the end would bring money as well.

"open themselves to have more developers supporting theirs?" -- Thats exactly what is missing from Google/Microsoft. Apple is already supporting Swift on other platforms, however, developer experience is not as good as on macOS and I don't think that can/will be solved by Apple. It is exactly where other players missing out, by making their dev experience as good or better, they could help developers write apps for their platforms.

They don't have to jump though, many iOS developers also do watchOS/macOS apps but they are still "iOS developers". If they can bring one more platform under their belt with little effort, I would say that many of them would consider it.

It's not a zero-sum game, they don't have to reduce support for other languages. It would be a completely new source of developers for these platforms. Better 1% than 0%, and I would say that effort for that would not outweigh the possible benefits and income from new devs/apps.

Those languages are already well supported on Apple platforms from the language makers themselves, there is not much Apple can do to "support them" better.

Opposite is not true though, there are lots of troubles you have to go through to have Swift on Android/Windows.

Very often, especially in startups, when the new app is created, it is first created for iOS and then for Android. Having proper Swift support would reduce effort for bringing apps to Android/Windows.

I feel like Swift is a big miss from Google/Microsoft. If they supported Swift on their systems (properly supported), they would immediately open up their platforms to lots of Swift developers, and I think the benefit would be more than they would need to invest into supporting Swift.