They also had a static workload, with no changing requirements, or really any need for scalability.

They also had FTEs with experience to configure the systems (which for a lot of us technical people is a no-brainer, but if you had data scientists with no hardware experience, that might be different)

This worked for them, and I'm happy for them.. the cloud does not solve all problems... It's simply one hardware strategy you can pick.. it's important to review the options!