Ops cost to number of server to manage is logarithmic but cloud cost is linear, so there's an intersection it starts to make less sense for cloud. Also equipment depreciation is tax deductible whereas cloud bill isn't. A year of EC2 instance bill is comparable to buying the equivalent server

Also there are vendors renting out datacenters so you do less of hardware management.

Having worked at two companies spending 250M+ on cloud bills alone, they try hard to decouple from cloud but many things are vendor locked

Hybrid has been the answer to both. It shouldn't be a binary decision. stateless compute workload can fairly easily be offloaded to private cloud.