Reason: we (our unit-tests and QA team) never test this scenario. Also it's not important for us.
So, let's fail in this case: if local preverified.toml doesn't exists and remote can't be fetched (by any reason).
Error message must be clear (with url and error details) and actionable by our users (like try re-start, try set own url by cli parameter, etc...).

Follow up: "erigon can't finish download files" fixed by #12403