I saw what you saw.
It wasn't so much a "bobble" as it was the ball never getting seated properly in the glove until after the runner's foot hit the bag. But the umpire was in no position to see that even if he was quick enough to notice what we noticed on slo-mo replay. The umpire blew the call but he may have accidently blown the call right. It would depend on the strict definition for what constitutes a "catch" at first base.
In the outfield, for example, an umpire won't rule a "caught" fly ball an out until the ball is successfully transferred to the throwing hand. That rule has led to some really stupid calls and needs to be tuned.
Rule 2 defines catch:
A CATCH is the act of a fielder in getting secure possession in his hand or glove of a ball in flight and firmly holding it; providing he does not use his cap, protector, pocket or any other part of his uniform in getting possession. It is not a catch, however, if simultaneously or immediately following his contact with the ball, he collides with a player, or with a wall, or if he falls down, and as a result of such collision or falling, drops the ball. It is not a catch if a fielder touches a fly ball which then hits a member of the offensive team or an umpire and then is caught by another defensive player. If the fielder has made the catch and drops the ball while in the act of making a throw following the catch, the ball shall be adjudged to have been caught. In establishing the validity of the catch, the fielder shall hold the ball long enough to prove that he has complete control of the ball and that his release of the ball is voluntary and intentional.
He caught the ball at first.