Tell me what do you think would have happened if they didn't lock down the town. Remember these guys were tossing explosives at cops and they even killed one on MIT campus.
Caught
sooner. Remember, the remaining guy was holed up in a boat that the owner was prevented from accessing during the shut-down.
Also, pipe bombs, not nukes. Pretty weak tea, otherwise we would have been issued pipe bombs and not frag grenades back when I worked for Uncle Sam. Also, more (realized and potential) bomb-throwers get kersplodied by their own chemistry experiments than do innocents, when they try to cook up the more potent explosives.
There was no good reason to lock the town down,
especially after determining the threat level. They killed fewer people at the marathon and afterwards (up to the capture of the second suspect) than Chicago's murder rate projects for a similar number of days. If they got lucky, they would have
matched Chicago's murder rate for their days at large. The difference lies in the sort of person killed and means. Nobody gives a damn about thugs killing thugs in Chicago (or Boston). But kill middle-class marathon-goers and you get the city shut down, armored vehicles rolling down the streets, and puffed up mall ninjas ordering taxpayers from their homes at gunpoint.
