Strawberry is free software and open source, it was supposed to be a collaborative community effort, but for over 6 years it's been mainly me doing most of the work, which is why it has been a lot more work for me than expected. For long periods I've even worked on it for like 7 hours a day and more in addition to a full-time job working into the night. For all these years, there have not been many days where I have not worked on something related to Strawberry.
If there had been more developers willing to spend a little time on helping out with things such as issues that are reported, it would have been a lot less work for me, but this hasn't happened, even many users said they would contribute never participated at all. Occasionally there have been a minor contribution from someone else, but that's been rare.
For macOS there have been 2 developers who helped for a short while, but the things that were done were pretty minor, as for Windows it's been 100% me since the beginning of this project. To continue support both macOS and Windows a little funding is necessary.
Only a few users donate anything unless the downloads are restricted, it's not the most ideal solution, but it has actually proven to work better, since the donations have increased.
At some point I got to make a change, and I felt like the 1.1 release was the right time, since it fixes some design flaws that have been there since the beginning, it's well worth the upgrade for users, and there is a good reason to spend the money.
Linux can't really be compared, since I do not have to maintain building all the libraries too, as those are already part of the Linux distribution, and most Linux distributions already have strawberry in their package repository, they require only the source code. And I won't close down the source code, it will stay open.
The Linux downloads on the website and GitHub are mainly there because it's part of the continuous integration to test if strawberry builds and to easily test new code, so I might as well distribute them, but very few users actually need them since strawberry is already part of the Linux distribution anyway.
I could create something like AppImage for Linux which would be closed like macOS and Windows are, I asked if someone is interested in paying for that, but no-one has replied, and I doubt anyone cares to pay extra for that since they can just install strawberry from their package manager in their distribution.