I think Chelsea is focusing more of their energy on the premier league compared to the league cup because they want to reach a better level by the end of the competition. I think Pochettino was targeting a top 4 position in his first season with Chelsea and they have been able to improve their performance in their last few games. Currently chelsea is in 10th place in the standings and they are 8 points adrift of Liverpool in 4th place.
Even when it is looking like Chelsea is focusing most of their energy on the Premier League games, I don't think they ought to abandon other competitions. What I think is happening with Chelsea is that they are building the confidence of the players considering that they had a very bad starting this season. The recent form they are picking needs to be sustained if they have to finish this season well. You know morale is very important in sports since consistent winning is built on this.
With time Chelsea will go back to being a formidable force, this is a possibility. Their time of woe seems to be over and the players are playing with so much excitement amidst good support base.