If Parler had done this, the ways they could have been "destroyed" would have been:
1. refusal to provide DNS for their address
2. refusal to certify an SSL certificate (not absolutely required but more than just a detail in 2021)
3. refusal by an ISP to carry their bits
I believe that even the progressive end of the tech community would have been extremely negative about any company that did any of these 3 things. I also think its very unlikely that any of them would have happened, though the Gab case provides some evidence to the contrary.Instead, Parler followed the unfortunate dumbification of online presence over the last 20-30 years, and instead of doing the above, contracted with a large corporation to take care of things for them. The large corporation decided they didn't want to do that anymore, and Parler lost its online presence.
Parler is not exactly unique in having made this choice. But perhaps the consequence of the choice they made might convince more people/organizations/corporations to think a bit more clearly about the type of hosting infrastructure they really want/need. If Parler had followed the self-hosted pathway, I think it is extremely unlikely (though sure, not impossible) that they would be offline at this point.