The first factor was the rise of the DVR, which has made it cheaper and easier than ever before for people to record their favorite shows and watch them at their leisure. This has been great for television artistically, since it means creators can now more readily assume that every single episode of their show will be consumed in sequence.
Stephen Johnson's book "Everything Bad Is Good For You" analyses the complexity of TV programs from the 1970s and today and shows how much more complex modern ones are. Compare Columbo with one murderer shown at the start and it takes 70 minutes for them to be found out. Whereas a more modern CSI is 43 min of multiple plots with loads of characters.
The Vox piece points out that episodic series like CSI with few series long story arcs now seem outdated. Viewers are expected to keep information about longer plots now. Meaning there are more details about the characters and their relationships viewers need to track. Series you can play back at any time may be cognitively as well as artistically beneficial.