What really progressed the case was the Undisclosed podcast [0]. Rabia Chaudry, a childhood friend of Adnan and an attorney, first took Adnan's story to Sarah Koenig, who documented it in the Serial podcast. But in Undisclosed, Rabia and her colleagues Colin Miller and Susan Simpson dissected the case with scalpel, found new evidence, and ultimately set the groundwork for today's result.
Undisclosed stuck with it, and have covered other similar cases. Their twitter [1] says they've had 400m+ downloads, which is more than Serial, albeit over many series.
If you liked Serial, or even if you didn't but do like True Crime, go check out Undisclosed.
If long podcasts are not your thing, HBO's The Case Against Adnan Syed [2] is quite information rich across just 4 episodes.
[0] https://undisclosed-podcast.com/episodes/season-1/ [1] https://twitter.com/Undisclosedpod [2] https://www.hbo.com/the-case-against-adnan-syed