I was skeptical when we signed with ETH because he came from Ajax from a "minor" league where Ajax was clearly the best team.
But for the same reason, I am again skeptical. Amorim, like ETH, comes from a "minor" league where his club, Sporting, is the best team.
It will be completely different to get to the PL, where United should perhaps be among the top 6-8 teams right now. And there will be teams and managers who are at least as good.
I would have preferred a manager with PL experience who had already shown results despite there being better teams than his own in the league. For example, Thomas Frank from Brentford, who has achieved good results with a small budget, even though most teams in the league are better than his own.