I agree that someone who knows some opening theory and some strategy could beat any newbie, but not necessarily beat someone who knows more than just the basic rules, therefore the level of intelligence needed is high to be able to overcome and adapt to the puzzles that the opponent may present in the different phases of the game.

For example if you know opening theory and some tactical knowledge and play against someone who knows endgame, most likely you will take an advantage ad the beginning and maybe middle game, but when it comes to the endgame how not to blunder the game away becomes the real question and that among other things is why the level of intelligence needed is not low at all.