Why Did This Japanese Politician's Gundam Cosplay Receive So Much Backlash?

In the campaign for Japan's recent upper house elections, Taro Yamamoto, the leader of the Reiwa Shinsengumi party released a sketch-like video in which he cosplayed as Mobile Suit Gundam character Quattro Bajeena. However, this move attracted backlash from many Japanese commenters on social media, and prompted the anime franchise's production studio to release an official statement denying their involvement.