Como might be considered a weak club by you, but what they did to Napoli was the same thing they did to Milan, Fiorentina and Juventus. Como got all three points from these four strong clubs including Napoli, so I am not surprised. However, when you underestimate your opponents, you will end up been defeated. Napoli wasn't serious in this match, and it has cost them losing their position to Inter.
Underestimating the opponent and not being serious in the match is very fatal for any strong team in any season. Because the team that is considered weak does not underestimate its opponent and they themselves must be quite enthusiastic in playing the match so that all the efforts they have will definitely be used in the match. And the result itself is also quite clear that Napoli lost to Como who had been underestimated before the match started so Napoli had to experience a decline in position in the current Serie A standings.
That's one of the biggest mistake most of these top side normally does, they mostly underestimate the lesser side and sometimes they rest a lot of players which will eventually affect the balance of the team, but on the other hand, resting of players is well beneficial to a team, because it will help them stay fresh and fatigue wouldn't creep in when their is a much stronger test that lies ahead, but this loss to como was really unexpected, because como aren't that doing that well, but somehow Napoli should have taken heed to the fact that they beat fiorentina last week, but they thought that they will be too strong for them even though they feel relaxed, but that wasn't the case here.
As for Atalanta Victory against empoli, it was really a win with intent, and I was pleased that they didn't allowed the penalty miss by ademola lookman which gaspirini made a controversial statement about affect their form, kudos to them, winning five nil is not an easy thing.