Parler chose to use AWS for their hosting. When you build your company on someone else's platform, you're explicitly giving them that market power.
There is not reason at all to have your content hosted in the US if you felt its legislators or IT providers aren't up to par to your idea of what free speech represents. Credibility? Yeah, seems that the crediblity issues weren't exactly about the hosting provider.
The legislative and judicial system didn't say anything about Parler, and that's the core of the problem. Big tech acted by themselves to appease the new king.
AWS can say “we don’t want Parler as a customer” but they cannot say “we don’t serve black people on our platform” as race is a protected class while being Parler is not.