I think it’s also both the people making the tech decisions and the people implementing them simply don’t want to work on mainframes. I would 100% of the time prefer to work with an on-prem dc or colo using commodity hardware and OSS to mange it.

I get my pick of a billion different hardware vendors, they’re all interchangeable and interoperable, every problem I can possibly dream up has been solved a hundred times before. The skills are commonplace and transferable so hiring doesn’t mean convincing some poor desperate grad to get trained in the company script, hires will actually want the skills, and you can find senior people.