It's new to me that Hansi Flick led Germany to win the World Cup He was assistant coach of Jogi Low in 2014 when Germany became world champion, but he was not in the lead at this time. And he worked later for Bayern before he became national coach of Germany were he miserably failed. So, Barca could be a good option. Money will not be the problem. Barca will not find a cheaper option if they want to get quality.
Indeed he failed miserably as the national coach and he lost trust quickly. He lost trust much faster than Jogi, who was lucky enough to have some very patient people around him or otherwise they would have sacked him long before they actually did it. But they acted quickly concerning Flick.
But I think that Barcelona could be a project that is doomed to fail for any coach if they can't improve the player quality due to liquidity shortages. It rarely matters whether Flick is a genius or not, I doubt that he can bring Barcelona back on track.