Not really. What happens when you run a cloud on top of your cloud is that you don’t get to use any of their differentiating features and that winds up costing you money. Plus you have to pay for your own control plane when that’s already baked into the cloud provider’s charge model.

You're not switching cloud providers. Amazon's not going to suddenly decide to jack up rates for EC2 instances on you. So the extra complexity just isn't worth it.

There is a hypothetical "but what if we honestly actually really really do", but that's such a waste of engineering time when there are so many other problems to be solved that it's implausible. The only time multi-cloud makes sense is when you have to meet customers where they're at, and have resources in whichever cloud your customers are using. Or if you're running arbitrage between the clouds and are reselling compute.