The Dodgers are nearly at full strength
This might be the true key to the Dodgers' success. While JD Martinez hasn't played since the Dodgers took three of four games from the Cubs, the Dodgers' win streak has come with a nearly full-strength lineup. Max Muncy and Will Smith both returned (Smith from the IL and Muncy from the paternity list), and have anchored the middle of the order. And in another sense of the phrase "full strength," Mookie Betts and Freddie Freeman have both started to heat up (along with other players that will be mentioned later on).
Betts' average sat at .233 and his OPS at .760 at the end of the series with the Pirates. Since then, Betts is on a six-game hitting streak (which coincides perfectly with the team's six-game winning streak) where he has tallied four extra-base hits and eight RBI. Muncy has reached base safely in 10 out of his last 27 plate appearances, and came through with the walk-off grand slam on Wednesday. Smith had two multi-hit games in a row in the first two games of the series against Philadelphia, and has scored six runs since his return from the IL. Getting Muncy and Smith back has been huge for the Dodgers, and we haven't even mentioned the fact that Tony Gonsolin came back from his IL stint to bolster the starting rotation.