Queen wasn't knocked out, he played dead and came up with a plan to be more effective. These same blows, if landed completely. were sufficient to knock out everyone in WCI.
Queen dealt more damage to Big Mom than anyone else until now. He wasn't shown using Haki, no Hybrid Form or Cybernetics, just his pure strength in his full Zoan form. The blow was so strong that could make Big Mom's memories vanish/come back and feel massive pain.
Queen's overreacts towards every single thing and then he starts chilling out of nowhere, thats a literal character trait of his, since his introduction.
Dude was chilling a few panels later