I do not think that Real Madrid really "allowed" anyone to be the first, they are playing well, they haven't lost or got a tie that commonly, they are playing well, the difference is that Barcelona is playing even better.
This is why I believe that we are going to end up seeing Barcelona win the title this year. On the other hand, if Barcelona still goes on to finals and win Europa cup, while Real Madrid somehow manages to lose both domestic cup and UCL at the same time, then we are going to see Real focus only to league, while Barcelona focusing on many other competitions and there could be some trouble there for sure, which will create a trouble for them.
Both Real Madrid and Barcelona, both have the chance to win the championship trophy this season, only two points apart, making the competition between these two clubs even more fierce. however, the one with the most potential to win the trophy this season is still Real Madrid.
Madrid is one step better than Barcelona, although statistically Barcelona seems to be doing better in La Liga.
if Barcelona wants to win a title this season, what's more Xavi is targeting 2 titles at once. however, if he does not change the pattern of play and strategy. I'm not sure that Barcelona will be able to remain consistent in the following matches. the reason is, Xavi tends to rely more on La Masia than other players who clearly have better experience. Raphinha, who at the start of the season really relied on, but he didn't contribute at all. whereas, Xavi still has Ansu Fati who should be given many chances.
in essence, if the patterns and formations applied by Xavi are not changed. I'm not sure, Barcelona can win a trophy this season.