Think of it in this oversimplified way
1 out of 2 times they would make the 2 pt shot and send it to overtime
1 out of 2 times they would win in overtime
Net that means 1 out of 4 times (25%) they would make the shot, then win in overtime. Shoot the 3 and they win 33% of the time.
Actual odds of making the 2 are significantly lower than 50% (more contested, ref swallows whistle, loses ball, etc.) so this is being generous