You're going to pay the bill regardless, whether the employee is hired by your team or hired by the cloud vendor.
I don't know how management works through this math, maybe managing people gets exhausting and they just want to out-source it so leadership doesn't have to deal with it and then they can just focus on the core product.
And the above "I don't want to deal with it" reason isn't spoken of, the more more commonly touted benefit is cloud's "flexibility". Sure, but this is actually _really_ expensive. Every cloud migration effort I've experienced is only just worthwhile to begin to talk about because the costs are based on long-term contracts of cloud resources, not the per-hour fees. Nice flexibility.
With that said, the cloud may be a good place for prototyping where the infrastructure isn't the core value add and it's uncertain. A start-up is a prototype and so here we are. But, for an established company to migrate to the cloud and fire the staff that's maintaining the on premise resources.. I'm skeptical. More than likely, this leads to maintaining both cloud and on premise resources, not firing anyone, and thus, actually increasing costs for an uncomfortably long time.
And for the folks on the ground, who don't pay the bills, the increase of accidental complexity is rather painful.