I wouldn't be too sure of that and after all they hid it all this time, so there will be at least some who will seriously be pissed like the king and other high standing Persons, afterall in a way they put everyone in danger, when they experimented with a demon lord and called it god.
When they needed some new power source, they didn't even give the people Information like:"Hey mayby if we don't find anyone, then not only will all magicans lose their power, no we could even be invaded by extremly angry demons"
Or to make it short the people of the tower are greedy and egoistic so they will play dumb till the end so they can hold as much power as possible, without thinking about the consequences like many many people dying.