Atalanta is not an unknown team, they are one of the teams that can be counted on in Serie A, it's just that they haven't been able to fully put more pressure on Serie A. Maybe if their similarities when looking at teams from other leagues Tottenham can be an illustration of how they can play, yes they can compete but they haven't been able to compete even better.
People just didn't expect that they would be the ones who could become champions in the Europa League when they had to face 2 more favored teams, such as Liverpool and Leverkusen. This is actually a very common thing in football, a team that is not more favored does not rule out the possibility that they will be able to give a surprise.
I do think that keeping with the same manager for a long time does make it easier for a team to grow exponentially but they have something that will take a while. I think we should consider this as something that will take a while. I believe that we are going to end up with a great result one way or another, shouldn't really be a big deal at all. I know that it is going to get to a point where things will change a lot, it is going to be something that will take a while.
We should be considering the situation they are in and shouldn't really be dealing with anything at all. We are going to see Atalanta have some hard times in the future because they build the team to a greater place and then they lose some players that worth a lot and then they restart all over again. We can see them do fine at UCL this season or more likely that they are going to end up with a terrible situation. We should see this changing a lot over the years but will keep being good eventually.