This is because of Genome Hacking letting Mew ex copy their attacks and use them against themselves, oftentimes quicker and at a cheaper cost, such as when facing a Charizard ex
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Now the other big benefit to this variant is that this approach to the strategy can run both Foolish Burial and Nightmare Hand to get eventually your Skull Archfiend of Chaos into the GY, due to the existence of Transient Masquerader of Illusion (YGOrg Translation), a Level 8 Illusion monster that not only can Special Summon itself from the GY, but also send any Fiend, Illusion, or Spellcaster from your Deck to the GY
If you use it you pay the indicated cost - including returning a creature to hand
Those monsters specialize in preventing your opponent from making their best plays, but when your opponent does manage to Summon their best monsters, this new Elemental Lord can wipe them out