Liverpool have made a strong start to the season, with three consecutive wins giving them early momentum. While it's still early to say they'll win the Premier League, Liverpool's performance has been more convincing than Chelsea and Arsenal, who have struggled with inconsistent play at the start of the season.
Yes, Liverpool are the favorite for Premier League but i disagree with the fact that you said Chelsea are struggling to be consistent. Chelsea haven't lost a match out of the three games played so far, they've had, 2 wins and 1 draw the only difference compared to Liverpool is that Liverpool haven't drawn any game. Watch closely and you will see that Chelsea are not yet balanced, they are still work in progress but already defeating teams.
Teams struggling are Manchester City and Arsenal, if both teams are going to lack behind that means it's left for Liverpool and Chelsea to contend for the title.