Only Barcelona have a perfect points so far (9 points from 3 matches), no one would be wrong to expect them to become La Liga champions this season, but that's too soon to say, we haven't even go to the first El Clasico of the season yet, so even though Barcelona are currently having a good run, we can't know how they will be after that.
The interesting fact is that they always win the match with a score of 2-1. I don't know if this can be called consistent or Barcelona can win the match but actually they have a bad defense. Barcelona performed well collectively. Although they failed to get Nico Williams but Olmo has played quite well in the front line even though he played as a substitute. Lewandowski also performed very well with Lamine Yamal. It seems that Barcelona has found their rhythm this season.
on the other hand it could be that selling out their best players after that performed exquisite for the club at the end of the season wasn't in their original agenda but as a means to recoup money for the club where it's lacking some of these growing clubs have to be forced to sell their best players especially when they are faced with a juicy offer from the elite clubs
When a player performs very well in a mediocre club, there will be big clubs who try to make tempting offers to their best players. I think this is a common thing. Some clubs want to get profit by selling their star players. Some clubs are forced to sell their players because of requests from the players or the players' agents to sell them to other clubs. It is difficult to refuse offers especially if they come from top European clubs.