In fact, Chelsea was able to dominate the match compared to Nottingham, but Chelsea had difficulty breaking into Nottingham's goal. Lack of player creativity is the first reason, but a lack of consistent strategy is also a reason. I didn't find Nottingham playing well except being really good defensively which combined with taking chances, it won them the game even though it was completely unexpected.
The bottom team uses a defensive strategy to win points against the top team. The weakness of Pochettino's strategy is that he was able to find a solution to find the net even though they had a lot of shots in total. Poor finishing is also an excuse, but of course Pochettino is under pressure at the moment.
Statistically, Chelsea really controlled the match, but what would happen if they controlled the match without being able to score a goal, just as useless. Chelsea seems to have no confidence in the formation that the coach implemented. It was clear that the back three was not working, mistakes were made, but against Luton Chelsea were lucky because of their opponents. Chelsea needs four cb rear-backs, two wing-backs, then two wingers and three in the middle and one in front, with that Chelsea can attack more confidently, because Chelsea have full-backs who can be supported at this time.
Initially I really believed Chelsea would rise if Pochettino became manager, because I saw him very convincing during pre-season, even bringing in new players with promising talent. But after four games, my doubts returned. It turns out he couldn't utilize the existing players to make significant changes for Chelsea.