Russia does not want that bridge to fall. Ukraine likely does but wasn't able to execute (outside of artillery range by now, limited access to long-range missiles, utter lack of sea power in the area, failure to anticipate circumstances enough to take it out while they still had control over area). All other countries are trying to not get involved, including not selling Ukraine (many) long-distance high destructive power missiles.

I wouldn't generalize from that to "nobody could destroy a bridge".