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.