You forgot to include Stuttgart in your post of underdogs because they won the DFB-Pokal this season. I really love what plays out this season in English football, Italian football, and German football because the big clubs in those leagues will know that the small clubs are rising to challenge them, and if they fail to perform well, they won't win trophies.
After watching the performances across all leagues this season, I don't think there is any team to consider as a small club, each team has improved in different ways and strengthened their performance with top players, who could have expected Crystal Palace to defeat Manchester City in the FA Cup final because they have no history of winning trophy. Stuttgart won the DFB Pokal after 18 years, while Bologna won the Coppa Italiana to secure their first title in 51 years.
However, all unknown clubs have shown that they also can win trophies, it is not only popular clubs that can. I wasn't surprised that Bologna won a trophy this season because their performance was quite strong last season, they finished in a Champions League spot but did not go far in the competition, many people expected them to struggle after changing manager, but they won their first trophy in 51 years. Big clubs should tighten their belts, otherwise, we may see more weak teams winning titles next season.