Microsoft seems to currently be investing a lot of effort in making developing .NET server apps on a competitor's platform more capable, so I think it's not as cut and dried as that. If you develop a "good enough" LSP server for Kotlin, and have the "best of breed" tools in IntelliJ, then you potentially increase the pool of Kotlin developers, which creates network effects making Kotlin development more appealing, and then you see more IntelliJ use. There can be benefits to making your platform play well with your competitors, if you can still monetize the platform.