Dodger stadium has been renovated to encourage fans to move around for shopping, food, drinks, etc. It's almost like Disneyland now. More $$ spent. In that way its similar to Coors' Field in Denver. Party atmosphere. So the empty seats you saw can be explained a lot by that. Fans walk around watching the game. I think many new stadiums or renovated ones are headed in that direction. Ownership does not want fans just "sitting" there not spending money. It's still an entertainment venue. Years ago, when you noticed the fans, there wasn't anything to do but "sit".
Add to this is the fact that the game is in the middle of the week and getting in and out of the Stadium is and will always be a problem We don't have any worthwhile rapid trans system here to get people out of their cars and into the ball park. Our city is so spread out that it just takes an inordinate amount of time out of your day or night to just get in and get out. Moreover, playoff games just last so long because of all the managerial moves being made-much longer than the in season games.
Bottom line is empty seats at Dodger stadium does not mean they don't have a very loud, intense fan base. To conclude that would be a big mistake.
BTW: I saw an awful lot of empty seats in the Atlanta stadium too-especially in the expensive areas.