An MLB spokesman claimed that the use of Pujols' bat was "not a competitive concern," as reported by Marly Rivera of ESPN.
Instead, "multipiece bat failures that happened on the field" were the problem, which endangered player safety.
MLB prohibited this kind of bat in 2010, but Pujols was still permitted to use it. This is due to the fact that any player who competed before the 2010 ban was technically allowed to use the bat.
Game 1's second inning saw Maldonado get an RBI single. Later in that game, the Astros grabbed a 5-0 lead, but the Phillies tied it and made it go into extra innings.
As a result, the RBI single that Maldonado hit with Pujols' bat did not significantly affect the game's final score. When the Astros triumphed? Some fan bases' rage would have been insanely intense.
This explains why certain players are no longer permitted to use the bat, in case anyone was curious.