Popup in foul territory on the first base side. The pitcher is underneath the ball ready to catch it. The runner runs into him, 2 seconds later the ball lands in the pitcher's glove but he drops it. Is it obstruction? The runner was well outside of the normal running zone where he would be required to run if there were a bunt or a dribbler in front of the plate. i.e., he is well into foul territory when he bumped into the pitcher.

Obstruction?

Real Question is did the umpire think runner did indeed have contact with bag, that could be why he did not make the call and therefore beleived runner is safe. My quess would be umpire beleived runner did have contact with base prior to 1st baseman catching throw. 1st baseman would only need to tag runner if said runner made an attempt to go to 2nd base.