They would be the big ones
They have deep pockets, they have experience with large data centres due to their core product (Google and amazon) or exploit vendor lock in (Microsoft). They sometimes have stuff that can be run on prem, but severely limit options there (Microsoft with Azure and PowerBI is what I'm most familiar with there).
There's just no way a smaller company could have matched that in the beginning, and now we are long past any hope. Unless the businesses start to realise that the Cloud Act is dangerous to them due to e.g. GDPR (and other requirements). We face these problems, we have customers with sensitive data, and one of the requirements is that we host most stuff in house. So... Yeah, this might be a niche.