We learned from the last attempt that Times Square is under constant surveillance and police are always on scene. NYPD is much bigger and is on a different level when it comes to counter-terror.
That's really funny there
The last Times Square attempt was a guy parking a FRICKIN SUV in the square and running off. Even though you aren't even allowed to stop in the square, the SUV packed with explosives wasn't noticed by police. A street vendor (a Nam Vet) called the cops over when they saw smoke and heard firecrackers. Many minutes later. The only reason it didn't blow is because it was a dud.
A bomber leaving a pipe bomb or 5 all over the square would never be caught in time. They'd just drop it disguised as trash, push a button and BOOM.