One thing in particular struck me, apart from the pacing: There’s a lot of crying.
For a series that had a reputation for being artsy and weird and “post-modern” (I just remembered that one of the cast members was on some TV show at the time, and she said something like, “We don’t know what post-modernism is, but we think it’s really interesting.”), there’s a lot of very emotional stuff going on. Not only did people (many people, including one of the deputies) cry over the death of Laura Palmer — they continued crying (from time to time) over several more episodes, at least.
This is something you don’t usually see in mysteries — at least not the ones I read and watch — where there’s some grief (if appropriate) and then it’s mostly on to the investigation. Many times writers follow the Murder, She Wrote scheme (it certainly wasn’t invented by the writers of Murder, She Wrote, but that’s where I became aware of it as a trope) where the victim is pretty rotten and generally disliked.
This does two things for you, particularly if you’re working with the time constraints of an hour-long TV show — or a half-hour radio show. One: it enables you to eliminate most of the grieving — giving you more time for the mystery-solving — and two: it automatically gives you a lot of suspects.
This is not something I’m going to be using in the story I’m writing now. The victims were strangers to the detective and most of the suspects. But it’s something to be thinking about for the future…