He only created these bum Holy Knights so he could somehow wank the strawhats as an Emperor crew. On Egghead this energy was nowhere to be found around Kizaru or Lucci, where literally just 1 Admiral pulling up on them had the entire crew scrambling and shitting their pants.
Oda thinks he is slick, he just delayed the SH Emperor crew hype arc, people thought it was supposed to be Egghead but the opposition was too respected still. Hence the creation of these bums for the sole reason to allow them to flex.