If you look at the timing of the subs, you can see how the match was lost. Lewa was atrocious and we lost the press from the frontline not to mention he was off the pace.
Then 5 or so minutes later we go concede and a few minutes after that Oriol comes on. Premeditated but not the needed the sub.
I think if Pep's in change considering the bench and injuries then he is probably keeping the starting 11 playing for as much time as possible. Then dependent on who is tired, bringing on Giui or Raphinha for Joao Felix or Ferran to maintain the intensity in the press.
The Bellingham goal was a sucker punch for sure, a fast pace ball that is not easy to stop, but one that Stegen probably saves 7 or 8 times out of 10. But what went on tactically either side of that was everything wrong and lacking in Charly Herb's arsenal.