Crossplane could be one package that customers would not want to use directly from a major cloud provider. You'd never trust AWS/Google/etc to really give equal footing to a competitor. Separately, I'd prefer to trust the company behind the open source software as opposed to some other upstart. So this model may really work.
One observation: Crossplane and Upbound seem a little too unrelated of names. Github has benefitted from being almost synonymous with git (admittedly, Github also created the opening for Gitlab at the same time).
Great response! Regarding naming we did not want to tie the company to a single project, not did we want the project to feel like a vendor driven project. So we went with different names completely :-)