Inter don't have a very big gap in the standings... Don't forget that Napoli and Atalanta have no matches in the UCL... It's a very big pressure for Inter if they want to beat Bayern or get to the UCL final... But if they make a mistake, Napoli or Atalanta will definitely take that chance to take the lead... It seems to me that in Serie A it is not yet certain who can become the leader...
It is not certain but now Inter Milan are very much favored to win the Scudetto this season after they managed to beat Atalanta last weekend and that also proves that Inter Milan's quality is much better.
Regarding Napoli and Atalanta's undivided focus because both teams are not playing in the Champions League, I think it cannot be used as an excuse because Napoli's performance is quite bad now even though they are only focused on Serie A so it cannot be used as an excuse for big teams to share focus to win several titles.
Inter have a Serie A game against Udinese soon, then a Cup match against Milan, then an easy away game against Parma and then a UCL match against Bayern... Napoli don't have such a heavy pressure and they're not too far behind Inter in the standings... By the way I wouldn't say Napoli are playing badly right now... Just one mistake of Inter can equalise the chances of leading Napoli...
Although Napoli have not played badly this season, in my opinion they seem to have failed to take advantage of the momentum, because in reality since the beginning of the season they have only focused on domestic competitions, they should be the ones currently leading the standings. Apart from the tough opponents that Inter Milan will face in the next match, this also does not necessarily provide direct benefits for Napoli, because they may also make mistakes.
Inter Milan will face Udinese next week and Parma after that, while Napoli will face AC Milan and Bologna. Therefore, I think Napoli journey will be a little steeper, Conte must also be aware of the pressure that Atalanta continues to give. However, in general, Napoli performance this season is much better than last season.