loud assasination with collateral damage to send a message
If you really want to hate Russia for this, just remember that sufficiently advanced incompetence is indistinguishable from malice.
The more you read about it, the more you become in disbelief. If it was an operation, it is one of the most advanced ones that I've ever read about. They knew exactly how to deactivate beacons, avoid military radar, there was a power and communications outage (computer interference?), the airplane kept flying for another 7 hours (without detection!), there was no distress call, ... and so on, which cumulatively is extremely unlikely to occur by chance, and would speak to extremely knowledgeable and capable agents. The bodies were never found, so it is possible that the passengers were offloaded. Imagine going to those lengths just to capture one person, or a group? The only other time I've seen that level of coordination was with Edward Snowden.
Quite a big "if". I don't know of any reason to believe it was anything other than one insane pilot. One of the other things your "operation" has to do is plant the flight plan on the pilot's PC.
From my perspective, it's unusual to commit suicide in such a silent way, with such elaborate attention to detail. He could have killed the copilot, and had knowledge about disabling beacons, perhaps also about avoiding radar detection. But why? As an elaborate prank in creating the greatest mystery in aviation history?
Hijackings are usually far more loud. Distress calls, passengers contacting loved ones, a manifesto is published, or the airplane is destroyed defiantly (GermanWings, Q400 2018 incident, ...).
Everything about it is extremely unusual.
Of course you have to evaluate the facts yourself, but it's healthy to have some critical perspective.
You can have defectors internally in the country. In Russia, defectors have a tendency to fall out of a window, regardless of who might be walking on the street (collateral damage).