Its indirectly gravity. The taller the mountain, the more eroding force can be pleced on it. Water travels faster and therefore cuts deeper.

Everest is still uplifting fairly quickly at 1mm a year, but its also eroding at roughly the same pace and won’t get significantly taller than it is now. The same is true for the rest of the Himalaya as well, the whole range is eroding at a very high pace.

The Himalaya are home to some very spectacular canyons, including the largest canyon above water. The geology there is on full display and incredible.