According to WP, it was still pretty quick. They had about two or three minutes from loss of power to collision. That had the pilot assess the situation, call a mayday and request the bridge be closed, dispatch to order the cops to act, and them to act. Then it had to take time for the bridge to clear.

One cop said on the radio that as soon as he got the traffic shut off, he was going to go evacuate the bridge workers, which obviously they didn't have time to do, but that was still quick. I would not have expected that to have happened so rapidly.

https://en.wikipedia.org/wiki/Francis_Scott_Key_Bridge_collapse

Dali left the Port of Baltimore at 12:44 a.m. EDT (04:44 UTC) on March 26, 2024,[24] bound for Colombo, Sri Lanka.[25] Two local pilots were piloting the ship.[10] At 1:26 a.m.,[26] the ship suffered a "complete blackout" and began to drift out of the shipping channel (a backup generator did not power the propulsion system).[13] The ship dropped its anchors as part of its emergency procedures.[3] At about 1:26 a.m., a mayday call was made from the ship,[26] notifying the Maryland Department of Transportation that control of the vessel had been lost and that a collision with the bridge was possible, citing loss of propulsion.[1] One of the pilots requested that traffic be stopped from crossing the bridge immediately.[3][27][28][29] The ship's lights went out and came on again some moments later; the lights then went off again and powered back on immediately before impact as renewed smoke spewed from its funnel.[10][30] Following the pilot's request, Maryland Transportation Authority Police dispatch requested officers to stop traffic in both directions at 1:27:53 a.m. Northbound traffic was stopped at the south side after 20 seconds. Southbound traffic was stopped at the north side at 1:28:58 a.m., with less than 30 seconds before collapse.[31]

At 1:28 a.m.,[32] the ship struck a support column of the bridge, beneath its metal truss and at the south-west end of its largest span, at 8 knots (15 km/h; 9.2 mph).[11] AIS data shows the ship traveling at a speed of 8.7 knots (16.1 km/h; 10.0 mph) at 1:25 a.m. before departing the channel and slowing to 6.8 knots (12.6 km/h; 7.8 mph) by the time of the collision two minutes later.[30][33]