Nope. The Esc fan favourites of Sanremo were:
2019: Ultimo/Il Volo
2020: Gabbani/Elodie/Elettra/Rancore/Levante (Diodato was second half of the ranking in almost all the tops I've seen)
2021: Madame/Francesca & Fedez/Irama and, in minor part, Annalisa.
This were the fan favourites. Several tops are still online, you can see by yourself... Nobody knew Mahmood prior to Sanremo 2019, so nobody thought he was a winner: everybody thought it would have been between Ultimo and Il Volo (which came second and third). Nobody knew Diodato before Sanremo 2020: the hype was surrounding other names, even in Italy. But he won eventually. A lot of people knew Måneskin in Italy, they were hyped in Sanremo...but hyped by Italians, not hyped by the Eurovision fans. They started to like their music after a while...
I understand your reasoning but it has some flaws that I will explain briefly and schematically:
1) You don't have to look at the preferences of the European public but of the Italian public. It is not through the European vote that the Italian representative is chosen. For example, Elettra Lamborghini and Rancore (the latter I appreciated lukewarmly) never had any chance of winning the Sanremo Festival.
2) At the Sanremo Festival having a famous name has a relative importance. Among all the defects that our Festival can possess, the vote of the public which is always democratic. At the Festival the singers are all the same and if Vasco Rossi were to participate with a bad song, the Italian public would criticize him harshly and would even make him reach the lowest positions (this is the fate that has happened to many great singers). On the other hand, if a "stranger" manages to bring a good song he could have the chance to beat and surpass in the charts of the most successful big names of him. It 's true Mahmood did not know anyone, Diodato instead knew him in a few (if I remember correctly he competed in the past with Roy Paci) and ... they won! This confirms my words (which are always based on a critical observation of the facts - then I can be wrong sometimes too).
3) The struggle for the victory of the other editions was not as fierce as many want it to think. It is true that Ultimo and Il Volo were strong, it is also true that ONLY Gabbani could annoy Diodato, it is true that F&F (thanks also to Ferragni's followers) and Willie Peyote (to a lesser extent) were strong and Irama a little he was penalized but ... all the songs that have won past festivals were still too high and it was clear that they would win. This year there is an unsettling situation of balance. Anyone can win, there is no favorite.
4) Mahmood managed to bring with "Soldi" a first great revolution in Sanremo (a way of singing like this had never been proposed), Diodato managed to compose a high-level poignant song and the Maneskin have even revolutionized world music. It was clear from the first listening, at least for me, that they would triumph and even some eurofans, aware of this, for fear they started to heavily offend every aspect of their songs.
On the Maneskin, in conclusion, I tell you that I love them but in reality they have not done anything special. They brought back to life the Rock that had now become a forgotten genre. They have managed to bring back, in the midst of the majority of autotune, industrialized music and grotesque characters, the true meaning of being a band, singers and players. They mixed the genre Rapcore, Pop, Hard Rock, Glam Rock and Brit Rock (because the real protesting Rock is the British and American one) in one song and then they said a pretty clever phrase "Rock will never die" .. the omelette is ready! This made many fans drool and dream! However, their level, even if high, is still not at the level of the bands that have made Rock history. My nephew who lives in London, he is absolutely right, he said after listening to them "Ok ... they are strong but ... if I go to Birmingham I see a lot of bands like that". Well, if Ashley Wright had told me this I would have agreed with him. The only difference between Italy (first) and UK (last) was not strength but courage. If the UK had been able to maintain and exploit its great musical history now ESC 2022 would be in London.