You can see 2 fuses on the primary swinging down after both of them blew @ :9 sec. mark, maybe there was a 3rd phase, can't see. Most likely reason during fair weather is something highly conductive fell across the 2 phases, because normally they're not that loud when they blow.
And those two conductors start swinging at: 7 second mark, 1.0 second before the fuse blows (maybe), so it's possible the fault occurred somewhere to the right off camera.
It takes a second for the sound to hit your cam's mike but when can see the smoke and a crow at the top of the tree at top right hears it and flies off immediately!
I was a subway operator for several years. It wasn't super uncommon to have a motor blow when applying power from a stop. Always scared the sh*t out of everyone on the train and platform. It was like a rifle shot if you it was on the lead car.
600V DC being shorted produced a lot of noise and smoke.