The Spanish league is a very strong league. I think everyone knows that. Even if you are Barcelona or Real Madrid, it is possible to lose points in that league. You can get some defeats when you least expect it. This is exactly what happened to Barcelona. No one expected them to get defeated on their home field. However, they lost 3 important points in the championship race by losing to Las Palmas. Real Madrid was of course the team that was the happiest about this situation. If they win the match against Valencia, which they are currently missing, they will be the leader.
In general, La Liga is actually only dominated by 3 clubs, namely Real Madrid, Barcelona and Atletico Madrid. However, the competition is still quite pronounced because these 3 clubs can compete tightly and also other clubs can usually show a surprise in a match. One of them is as we can see from the Barcelona and Las Palmas match. No one expected that Barcelona would be able to lose like that and even when looking at the match statistics, Barcelona deserved to win. I myself also thought when they were 1 goal behind they would be able to turn things around. but the surprise really happened in this match.