Here's my think after just finish watching this series. This is sad and tragic, but for me NOT unusual. As a black man, I long lost faith in our entire judicial system and never trusted a pig ass cop. Therefore, none of this is unusual, because I heard and know of many times of stories where the police either try to go out their way to cover their asses when exposed of incompetence, or if a person or people try to either sue or expose a police force for corruption, that department would flip it to ruin, incarcerate, or destroy that person or group by any means necessary. The BIGGEST example of what they can do in all levels was what happened to the OG Black Panther Party and COINTELPRO.
With Steven Avery, this is a dude that for something trivial the police had it out for him when it was younger and set him up to teach him a lesson. Once, after 18 years, that police force got exposed. They were livid, and the fact that Avery was almost about to get 36 MILLION from that department and forever tarnish the credibility of that force among that citizens there as well as the entire Wisconsin state and RUIN the careers (with possible jail time for some of the key instigators).... they were desperate. They wanted to make sure this dude's life and everyone near him lives are RUINED. They needed him back in prison and this time ensure he stays there. So, I WOULD NOT PUT IT PASSED ANYONE OF THEM AS THE ONE OF THE ONES THAT KILLED THAT WOMAN just so they can incriminate Avery, and poor Dassey was just a bonus. I would further believe that it Lenk was the one specifically responsible being that he was directly involved in the accusation of planting evidence to begin with.
The most damning reason why I think this is because they KNEW about the "missing vehicle" BEFORE that woman was even announced missing. And based on the coincidence and timing of it all, her disappearing at the verge of dude copping 36M and a state bill being passed on his behalf, desperate men do desperate things, and wrongfully pinning on it before makes it easier to do it again.