How did the Hudson plane crash happen?

Answer 1

The plane suffered an extremely unlucky double bird strike after hitting a flock of birds. With both engines destroyed, their plane essentially a glider, the pilots weighed the limited options - from 3000 (?) feet, they did not have the range to execute a turn and return to laguardia. They also feared a failed attempt to reach teterboro across the river would result in massive casualties on the ground. The Hudson quickly became the only realistic option.

In control of the plane because his flight instruments were the only ones with power after the engines shut down (and reying on a ram-air-turbine deployed from beneath the plane for what little electrical power he had), the captain had to pull off something that few have ever done - land on the water without the plane breaking up. (Watch the YouTube of the Ethiopian 767 landing in the Indian ocean for an idea how ditchings usually pan out.) Because of a combination of dumb luck and skill, he was able to execute a controlled landing and the rest is history.