I personally think that at the end of one of the ice ages, and ice dam failed, allowing a catastrophic/biblical scale flood event that created the Grand Canyon, and most of the other spectacular erosion features of the area. (If you go, Bryce Canyon and Zion are FAR more awe inspiring. The Grand Canyon (to me) is just a really big ditch.)
You should read the article and also Michael Oard’s work as well. The Flood runoff stage involved the right amount of water and they outline the lack of ice age lakes in Arizona and NM.
But Harlan Bretzke DID show the ice age lakes in Montana carved out canyons up there.
We just gotta get the correct water in our minds for the correct canyons.