There isn't as many C# developers on Linux and MacOS because the experience has been terrible for a long time and still is lacking to a smaller degree, you have the cause reversed.
> Microsoft understands, among other things, that they can't charge money for Linux tools.
It's the opposite trend going on, they embrace as much as possible Linux and port as much as they can.
Since they just focus on Azure and just milk Windows with ads and let it rot nowadays, I'm guessing it must be very profitable, otherwise they would stop.
I'm sure Azure is profitable for Microsoft. Microsoft are not even trying to sell development tools (the category of tools that would include LINQPad) to Linux devs.
They don't care about development tools period anymore, they just make most of their business on the cloud and most of it being very dependent on Linux.
> Microsoft understands, among other things, that they can't charge money for Linux tools.
It's the opposite trend going on, they embrace as much as possible Linux and port as much as they can.