Atalanta was in a good form last season and that was why they were able to beat Liverpool and Leverkusen in finals to win the cup. The club sold some of their players and that affected the team performance. It is a shock to see how a strong team became so weak without playing matches. It seems that Italy teams can be very strong today and become vegetables tomorrow. This was what happened to Napoli too last season.
Honestly, Atalanta's performance was really good last season, but I don't think they had to be that great at the start of the competition. It was toward the middle of the season that their performance was well recognized, and they were in good form. Even this season, it is very possible that they will still do well. Losing matches in their domestic league doesn't mean that they are weak or that they won't improve later. The season has just started.
What people are worried about regarding their performance now is because they won the Europa Trophy last season. People's expectations are really high for the team. Even Real Madrid has dropped points in their domestic league, but that doesn't mean they won't win their league or even the Champions League. Let's see what happens in their upcoming matches.