was wondering the same, they could move all the Linux and save quite a lot of cost
They are "all in" on MS technologies. I followed them when they were building the system. Their sponsor is a 100% MS devotee (he's the father of VBA, for that matter) and there is no way that they would consider something based on logic. They were the pioneer user of the .NET MVC system and everything they have done is based on total lock in to MS, which has its advantages. But overall, they are using costly, slow components to do work. I'm sure that it works pretty well, but as good as it could? No way.
We've seen other communities like that make odd technology decisions leaving them locked in to old schemes and costing a fortune to do what is cheap with modern design choices.