Got this used bike for my son, issue is the crank is very high and for him to ride without his knees bending too much I need to out the seat very high, but then it's uncomfortable especially when he stops because he can't reach his feet on the ground.

I'm pretty much convinced to get another bike for him since this one was cheap, but what kind of bike is this? Why is the geometry so weird?

It's for grinding and to allow more chainring clearance in general. This bike is not intendet to have 'appropiate' seat height. Reaching your feet to the ground while seated is unnecessary. But this bike is designed to do just that, just not for seated pedalling. Anways nice try.

>>2040456 (OP)
>when he stops because he can't reach his feet on the ground

You're not supposed to be able to easily reach the ground while seated. Every time you stop you're supposed to dismount, stand on one pedal, and swing out one leg as a kick stand.

>>2040478
That's stupid oversimplification. Average people will find that most 700c bikes of ordinary geometry behave like that. No touching the ground, at best with the tip of your toe, while seated at proper seat height.
On the other hand there is plenty of geometries that allow some riders to put both feet down, at proper seat height.
There is no 'supposing' of feet touching or not touching the ground. It is merely a function of bb height, setback and rider physiology and commonly observed that at correct seat height putting feet down like that is not possible.