No conspiracy talk please.
The ship had a catastrophic electrical power failure as it approached the bridge. Wind and tide caused a radical and uncontrolled change of course (see last two Suez canal accidents).
Key Bridge was very old and under constant repair every day for at least the last 30yrs.
It could not have been a better time for the worst to happen. Hour and a half before rush hour. Casualties should be light. Mostly from bridge repair crews.