>>45622841Pachirisu was used because it had very specific qualities that synergized well with his team. Rage Powder didn't work on Grass-types (ie. Rotom-C) or mons with Safety Goggles, while Follow Me does. Park had two Flying-types, so having a Volt Absorber kept Electric spam in check for Talonflame (which it also checks beautifully due to resisting Flying and running a physically defensive set) and Gyarados. It could also spread status with Nuzzle, which always inflicts paralysis, is 100% accurate, and cannot be denied via Taunt, and can use Super Fang to chunk out bulky mons, so it wasn't completely passive.
If it lacked even one of those qualities, it would've probably never been looked at.