They were going over budget so they cut a few episodes and rewrote the 10th episode to make it a season finale, when it was supposed to have 13. It's similar to what happened to Tom King's Batman run recently, it was supposed to go for 100 issues, but the higher-ups apparently didn't like it, so King was taken off the book after issue 85 and given a subsequent 12 issue Batman/Catwoman limited series to finish his story, meaning he would get an overall 97 issue run as opposed to 100, same way Swamp Thing gets 10 episodes instead of 13.