I think everyone trusts the manager - but that doesn't mean every decision the manager makes is the right one. And it certainly doesn't mean that every fan agrees with every decision. ETH makes a lot of mistakes, but he makes a lot less mistakes than what every person in here would have done in his position. That is why he is the manager and we are fans. But that doesn't mean that every decision he makes is better than the one 5 random fans in here would make. If ETH makes 100 decisions during a game, maybe 95 of them are correct and 5 are wrong. But that also means that someone in here can point out that he did make a mistake in 5 situations.
Or maybe ETH made the right decision but the outcome still ended up being wrong. Take the Casemiro yellow card against Palace - a lot of people wanted ETH to rest Casemiro so he could play against Arsenal. For 80 minutes ETH's plan worked perfectly - we were 1-0 up and Casemiro did not get a yellow. Then both things backfired. But - if we hadn't played Casemiro, we might have lost against Palace - and we might still have lost agaainst Arsenal.
Add to that - we haven't got the information ETH has. We can complain about not signing a player, or about a player we actually signed. But we have no idea what options are available both in terms of money and players. For all we know, the board may have told ETH we wont sign any more players unless we can get the player on loan. Or the board may have said - we can sign this and that player if we can find a cheap option. Regardless, ETH saw Weghorst as the best option. If that was correct, it's impossible to tell. There probably are 50 players out there who would have been a better option that Weghorst. But its impossible to say if any of them would have available, and available as fast as Weghorst was. So maybe the 50th best striker was the first who fit the criterias: a) affordable b) available c) physical presence d) could make immediate impact rather needing time to adapt.
So some fans might actually get it more right than ETH once in a while. But I think most fans understand that ETH will get it more right a lot more times than some fans will - and that is why he is our manager, and that is why the majority of us trust him a little more for each win.