I personally think this was an act of sabotage by the Ukrainian GUR.

This Tu-95MS strategic bomber was flying with a full crew (7) and was likely equipped with Kh-101 cruise missiles ahead of the upcoming attack, redeploying to Olenya Airbase. The Russian Ministry of Defence claims that the aircraft was carrying out a training mission, but it would be an unusual time for this considering the next large-scale missile attack on Ukraine was expected to occur soon.

It also seems EXTREMELY unusual that 3 out of 4 of the engines would fail simultaneously, right after take-off. That happening practically guarantees the crew is killed, as there is no time for parachuting to the ground, which is another potential sign of sabotage.

Who knows if it truly was sabotage. We will probably see a statement from the Ukrainian GUR soon if this is the case. It's likely that all other aircraft at Ukrainka Airbase will be thoroughly checked for any signs of sabotage now, probably delaying the next large-scale missile attack.