Felix has been popular before he joined Barcelona. He was one of important players in Atletico Madrid, he contributed well for Atletico Madrid. If he wasn't quite popular and did no contribution, Barcelona will never sign him.
In addition to being popular, his skills are also quite good after being bought by Atletico Madrid so that he became an important player, but entering several seasons he lost his place in the main team so that his popularity began to decline over time until finally Barcelona loaned Felix.
Atletico Madrid and Chelsea are not the main purpose for Joao Felix, and Barcelona financial problems that made him have to leave have also been well accepted, now the most important thing is that Joao Felix can help AC Milan to compete until the end of the season in an effort to improve the standings.
He was likely having a problem with Atletico Madrid coach, so he was loaned to Barcelona. And after he failed to have a permanent contract with Barcelona, Chelsea signed him. Unfortunately Chelsea has too many players in attacking line, so Felix can't play regularly there. It is a better option to get a loan contract with AC Milan.
At Atletico Madrid he had problems with the coach so he was more often on the bench so he was loaned to Barcelona, but unfortunately when he played at Barcelona he again failed to reach the core position because of a lot of competition with his teammates, it didn't end there because even when he played for Chelsea he also experienced the same thing and had difficulty breaking through as a core player which resulted in him being loaned back to Milan.
Now is the opportunity for Felix to improve because at Milan he might get a position as a core player if he continues to give good results for the team.