The guy is an online gamer, a Navy vet, and a former sonar-man on 688 boats.Watch the video Modeltrains posted. (Who is the guy in the video by the way?)
Doesn't make him right or wrong, just answering the question. I'm not sure the source of the blast is relevant beyond satisfying our idle curiosity.
Bridge was a legitimate military supply-chain target. Ukraine labored to undermine the bridge, and had partly succeeded.
Russia responded by escalating attacks on the civilian infrastructure in Ukraine.
The world yawned in response.
In a few days Russia-lovers will return to blaming Ukraine and USA for "forcing" Russia to invade Ukraine and go medieval on its citizens.
Wash, rinse, repeat.
P.S.: The observation that Iranian suicide drones are now being flown by Russians out of Belarus, certainly opens Belarus up as an active combatant (if it wasn't already).