This is the paper mentioned in the video, it works out the theoretical maximum height of a mountain, not taking into account any geological considerations such as how it could get to be so high or depth of the crust supporting it. As an example at the end, they work out that a mountain made of granite with a base of around 1,000 km could be as much as 45 km high.

But they say it could be much higher if the mountain gets rapidly steeper as it gets higher, like the Eiffel tower.