Inter, having failed to play well in their recent matches, lost the Champions League final and the Scudetto. They had played very well throughout the league, but they couldn't finish the game as they wanted. They suffered a heavy defeat in the Champions League final, and that defeat led to their manager leaving the team. Now Inter is moving forward with a new coach. There are major question marks about what they can do this year. No one is certain of Inter's capabilities right now. I think they will be in the title race, but they may not go far in the Champions League.
That is the worst part about their season. Lose to Milan (Milan was terrible last year) at the cup, lose to Napoli with very tiny points difference at the league, and lose to PSG at UCL finals game. Looking at how they are, we could simply say that they were doing terrible as a result, like at the end they won nothing, but when you think about how they played all year long, they could have won 3 titles if they won 3 more games.
It's that simple, beat Milan to possibly win the cup, beat one more team instead of lose at the league, and beat PSG, that means, just three more wins all season long instead of losses, and they end up with 3 titles instead of one title. That type of season hurts a team big time, and makes it hard to recover.