Not him, but if I had to guess, it really WAS to keep anons thinking all of Trump's jarring policy moves over the last 2 years that seemed to be of no benefit to America at best and willingly put the citizenry in danger at its worst to keep us from rashly going into the streets like lynchmobs chasing down every Washington DC Democrat like the Yellow Vests are trying to do.
Think about it this way: If Q never visited 4chan to clue us in on everything Trump has done up to this point, most of us would either be full blackpill and ready to jump off bridges, or in full pitchfork/torch mode trying to track down Hilary and getting jackbooted by the Nat-Gs in the process through a total misunderstanding of Trump's intentions/plans to undo this corruption.
It's kinda like that one episode of Looney Toons where Bugs Bunny disguises himself as Cecil Turtle to win the race, and all his rabbit companions aren't clued in on the plan and start attacking/sabotaging Bugs as IF he were Cecil instead, making him lose miserably at the end.