We'll see, but perhaps there was some Russian involvement.
Now that the plane has arrived at the intended destination (Vilnius), it was missing two Belarusian citizens (Protasevich, and presumably his girlfriend who was on the flight has also been arrested) and four Russian citizens. There are some rumors that those four people were trailing Protasevich before the flight and were involved in the 'bomb threat', so it might as well have been a common Belarussion-Russian operation, but as of now it's all just guesses and speculation, perhaps tomorrow we'll have better info.
Belarus can't be closer to Russia than it is already - they effectively don't have a border between them. Belarus is a definition of a satellite state.
That's not quite true. Their relations have had multiple ups and downs. Besides, Belarus having burnt other bridges always offers Moscow extra leverage.
Russia, through Putin, and Belarus, through Lukashenka, are very closely allied. Highlighted in the NYTimes coverage:
It underscored that with the support of President Vladimir V. Putin of Russia, Mr. Lukashenko is prepared to go to extraordinary lengths to repress dissent....
In Russia — where the state media described last year’s uprising against Mr. Lukashenko as a Western plot — the arrest met with approval among Mr. Putin’s supporters. Margarita Simonyan, editor of the pro-Kremlin RT television network, wrote on Twitter that Mr. Lukashenko “played it beautifully.” And Vyacheslav Lysakov, a member of Parliament allied with Mr. Putin, described Mr. Protasevich’s arrest as a “brilliant special operation.”
To clarify the implications for Western readers who don't know how 'Eastern' state media works - it would be expected that media like RT/Simonyan would comment only the "proper" opinion and so on sensitive geopolitical issues the news agency can express a strong opinion only when Kremlin has decided on what the proper opinion is, they don't have the authority to decide on their own, the foreign ministry decides the proper message.
In earlier cases with genuinely surprising events they have refrained from commenting for sometimes quite a long time. The fact that they congratulate Lukashenka so quickly suggests that they were able to get a rapid confirmation from officials that this should be promoted instead of condemned, and it suggests that more likely than not this wasn't a surprise for Kremlin, that they were informed beforehand or perhaps even participated in making that "brilliant special operation" happen.
