I don’t really understand your point here but sometimes a team might have a bad performance in their domestic league and still perform wonderfully well in the champions league take inter milan last season’s performance as an example, they didn’t perform too well in serie A but suprised the world in the champions league. Some teams may perform well in the league but fail to perform in the champions league just like barcelona did last season.
I think comparing the two leagues and seeing the one that is more important and highly recognized which is the champions league, watching how they performed last season was impressive no one expected Inter Milan to succeed the way they did, and even make it to the finals, in fact, my calculation in the finals was real Madrid against manchester city they had a better chance to have won the champions league but they gave it away to manchester city since all attempt to score failed. and it is always difficult for some clubs to play well in all participating leagues always a difficult one to manage.
I think it was meant that if you let's say you lost points at the beginning of the season, then in such a fleeting tournament as the Champions League it will be difficult to then catch up by improving your game and results. As for a successful game in the national championship and an unsuccessful one in your own championship and vice versa, I would like to say the following, that this is very often a matter of priority, that is, if you missed the chances of a title in your own championship, then you can give priority to the Champions League games if everything is much more successful for you.
And in addition to what you saying, the issue of adding points is one of the strategies I have noticed that manchester city uses against other opponents, At the beginning of the season and the middle of the season they keep accumulating points, once any club fails at the beginning of the season it becomes more difficult to keep up with, priority to is involved and aside that there other factors that contribute to the success of the club talk of teamwork and other factors that is what killed most of the teams during the league.