You can target one face-up monster on the field once per turn that loses 500 defense and attack, with your opponent unable to activate cards or effects in response to the activation of this effect

Afterburner Expert Al Bhed Salvagers Beamsaw Prospector Biomechan Engineer Cid, Timeless Artificer Cloudsculpt Technician Curator of Sun's Creation Daretti, Rocketeer Engineer Daring Mechanic Dauntless Dismantler Draconautics Engineer Edgar, King of Figaro Elvish Archivist Fire Nation Engineer Forensic Gadgeteer Gadget Technician Geological Appraiser Greasewrench Goblin Guidelight Synergist Harried Dronesmith Inventive Wingsmith Iron Hills Blacksmith Kylox, Visionary Inventor Lake-town Toymaker Mechan Assembler Memory Guardian Meticulous Artisan Mica, Reader of Ruins Molecular Modifier Nimble Thopterist Oltec Archaeologists Oltec Matterweaver Oviya, Automech Artisan Possibility Technician Rishei, Getaway Accomplice Saheeli, the Sun's Brilliance Sami, Ship's Engineer Sami, Wildcat Captain Sandstorm Salvager Selfcraft Mechan Shuri, Wakandan Inventor Station Monitor Sunstar Lightsmith The Mechanist, Aerial Artisan Tony Stark Voyager Quickwelder Vulture, Scheming Scavenger Weapons Vendor Weftblade Enhancer Weftstalker Ardent Whiplash, Vengeful Engineer

Potentially, this might be exactly whats happening here, or Gwenom may simply be overpriced
Pikachu's universal appeal as the franchise mascot combined with the "last chance" energy of a closing-era set created strong incentives to grade, and the population data reflects that urgency