Would not be surprised if this was a Russian inside job; just one section was collapsed and pretty precisely - leaving the other road operational.
the other bridges taken out had holes blasted in the platform or the supports blown up.
I did wonder - there seems to be a lot of infighting currently and if it was a truck it was coming from the Russian side and the more likely direction for any kind of missile, etc. based on the footage is from the Russian side - possibly supposed to be a shot across the bows by one or other faction within the Russian regime which did a bit more damage than intended. Though I think a Ukrainian attack is probably more likely.