What this series really comes down to is the disconnect between the federal and local investigative authorities. Having "Tetris" in the name is somewhat misleading. Beyond investigators trying to put the puzzle together like a Tetris game, the case has very little to do with that at all.
If anything, I wish they'd spent more time on why the Russian mob would have killed Vladimir and his family. A theory was suggested a few times, but it wasn't explicitly laid out until the very end. And even then it seemed thrown together on a whim imo.
I honestly think the police knew more than they let on throughout the series. During the episodes Sandra surprises them individually with some of the info she's learned, which feels like we're finally getting somewhere. But when they meet later as a group, she "surprises" them with much of the same info again and they pretend like they've never seen it before lol. So you can never tell what's sincere versus what's being staged for dramatic effect. In that sense, if you want to enjoy Ep 3 you'd better hope you forgot what happened in Ep 2 because you might just be seeing some old re-packaged as new.
Another frustrating element was how the script focuses on whether the Feds already had a file open on Vladimir at the time of his murder in 1998. Debate on whether they did or they didn't is a point of focus that spans the entire length of the series. Now I'm no detective lol but in Ep 2 they flash on-screen the FBI's response to her Freedom of Information request, where it says in the Subject line: "Pokhilko, Vladimir 1994-1999." Just from those *dates- if not from the seat of my couch lol- you see the Feds candidly admitting they were on him for four years before he died, and then for another year afterwards (possibly until the evidence was destroyed?). Yet the filmmakers continue to act dumbfounded as to how the FBI/DOJ could have been so responsive to his death in 1998, how the District Court took just two days to issue a subpoena, etc. Yes they were watching him! They told you they were watching him! Can we stop acting like they're hiding it?! It's little gaffes like that that lead you to think the series was produced more for our entertainment than to get actual answers to questions.
For that matter, if you were to ask me why it was deemed a murder-suicide, my answer would be similarly boring: that's just how cases like this are handled. This was a Russian family in the United States (presumably not American citizens yet) who got murdered by Russian hitmen. To what end should American time money and energy be used in an investigation, right? If you look at it that way it makes a lot more sense. Not that it's not dirty or controversial but authorities were looking for any excuse to close the book on it as soon as possible. Because despite the fact it happened on American soil, it wasn't technically an American problem.
And again, it's not like I'm Sherlock Holmes here. I think the police understood that as well. The drama was just sort of manufactured in order to produce a documentary. Fake true crime, if you will. Which is fine. I enjoyed parts of it too. But I wonder if it's not a microcosm of our relationship with media today, and how we're watching a lot of make-believe investigations. Even if they're done with good intentions, sometimes it seems they're conducted more to conceal the truth than to uncover it; more to obfuscate than to educate.