The math going for 2 when scoring a td down 14 to cut the lead to 6 is all about winning the game in regulation.
The math on getting a successful 2 pt conversion is nearly 50/50. So if you for 2 on the first td, and its successful your chances of winning in regulation improve dramatically. If you miss you go for 2 again and statistically you have a better chance of making it after missing 1 already