Interception Touchback/Safety question

[Striker991]

I'm not that familiar with football, as I am a baseball guy. Reading this forum has helped me understand the game immensely. Many times I have seen a play and actually understood why a call was made due to this forum. Watching my kids' highschool game this last week, I saw a play that I have a question about.

Pass intercepted by defense on their own 2 yard line. Player having made the interception takes at least two and maybe more steps along the 2 yard line before either his momentum or that of the other player carries him into the endzone where he hits the ground, holding the ball securely.

The call made by the official was a touchback, which benefitted the intercepting team immensely (our team). The ball was placed on the 20 and played from there.

My questions are: What might have been the reason for the touchback? Why not place the ball on the 2 for the intercepting team's possession? Why would this not be a safety if he carried the ball into the endzone?

Thanks for helping me to better understand this call.

Striker