The lever is not broken.
The lever's job is to pull the cable away from the brake.
There are springs in the brake that should pull the cable away from the brake lever.
The cable housing should allow the cable to move back and forth with as little friction as possible.
Since it was working before the crash it makes sense that something was bent, kinked or damaged restricting the cables ability to move. Your hand is able to overcome the friction when you pull the brake lever but the springs on the brake are not strong enough to pull the cable back.
It boils down to sticky cable or weak springs. Chances are it's the cable because a crash usually does not weaken springs.
From the video it looks like you have a v brake
Things to check: You may want to disassemble the cable from the brake to isolate the problem.
- Make sure the brake arms are moving freely but not sloppy. The mounting bolts should be tight without restricting movement of the brake arms.
- Make sure the cable can move smoothly in the cable housing and in the cable guide.
- Any cable housing kinks, hard turns, or incorrect cable installation will restrict cable movement. You want smooth bends and low friction along the whole route.
- Sometimes a little silicone spray inside the housing helps even when the cable housing is lined.
Sometimes you can increase brake spring tension with the balance screw.