I wouldn't say Pochettino did a bad job. He is progressing well with Chelsea. Chelsea may not win well in the first two matches. But their performance is not as weak as last season. Their performance is very organized. Pochettino has worked to strengthen the bond between the players. But the problem is that Chelsea's squad is still not strong enough. Chelsea's attack is a bit weak. Pochettino needs to add another experienced striker to the attack. Also Chelsea's biggest problem right now is their defence. They lost badly against West Ham because of poor defence. Chelsea conceded 3 goals. West Ham only had 24% ball possession in this match. They still managed to score three goals. If the defense cannot be strengthened, the expected good performance from Chelsea will not be seen in the upcoming matches.
If Chelsea performance has no change (still bad), how we can say Pochettino do a good job?
You admit that Chelsea still has weak attack and fragile defense. They even couldn't win in the first 2 matches in EPL. TBH, I don't see something different between Chelsea in the last season and the current season. Pochettino still can't build Chelsea properly, he needs to show us a positive progress. If there is still many problems in Chelsea squad, I'm not sure he will manage Chelsea a long time.
By the way, we can understand if Chelsea couldn't win against Liverpool. Got a draw is not a really bad result. However, defeated by West Ham with 3 conceded goals is something unacceptable. Although West Ham has some good players, but Chelsea squad should be stronger. There is something wrong with the tactics if Chelsea defense looks so fragile. Pochettino is the man who has the responsibility of this problem.