I don't think it was inevitable, last season there were good signs with obvious squad holes but also adapting needed on Ten Hags part address issues we saw in those big away games. It's just a case of how many chances do you give someone to address those issues. For me, Newcastle was the game when I decided I saw enough and came to the conclusion he just can't figure those games out.
Managers are never going to get it right, right away. They'll need to adapt, they'll need to address issues that opposition managers find in your system, especially in this league. But if you keep making the same mistakes, if your system that you are building towards keeps getting picked apart in a frankly pretty simple way, then that just points to the manager.
In any season, there are some good signs. For example, under LVG we went in a run of games when we played brilliantly, trashed City, defeated Liverpool in Anfield, and also Spurs. It was not good enough.
I am saying it was inevitable, because by September/October when you made this thread, it was already more than half a year of pure trash. We played quite good between the WC and League Cup final, but on both sides of it we were trash (especially after the League Cup). We were trash in the pre season, and despite that the results there do not matter, the performances kind of do. You can see that there was no organization whatsoever back then.
And ultimately, we fecked up in the transfer market. De Gea while way past it, has more talent than Onana will ever had. Mount at best is a squad player that a top club should get only if he is out of contract. And Hojlund, I have yet to see that he is anything more than a Championship level player, with journeyman EPL-striker potential.
We effectively downgraded the keeper position by replacing De Gea with Onana, and downgraded the midfield by replacing Fred with Mount. ten Hag sabotaged himself by creating a massive problem with Sancho in what was something that should have been solved in 2 minutes of a training, and then continued sabotaging himself by dropping Varane. We did not improve the attack, which was our main problem last season. Essentially, if I ever saw someone burning 200 million, this was EtH and United this summer.
The main problem is that I do not see any redemption, any silver lining on all this. After 400m pounds spent, and 18 months of coaching by what was labeled as a good coach, we are worse than before he arrived here. We are worse than at our worst point under Ole or Rangnick. That is really just sad and despite his League win trophy, I think that EtH is ultimately the worst manager we had in our lifetime. He was unconditionally backed, more than any other manager we had, and despite starting from a very low baseline, somehow managed to make us worse. Especially when you add that here the expectations were high (unlike for example Ole or Moyes where everyone knew that they will fail).