How is it possible to overwater plants in soil when some are grown solely in water?

Just curious as to why its so easy to overwater when some plants are grown hydro

Weed doesn't like to have "wet feet", and the roots need O2. In hydro not all the roots are in the water(so they get air), and the water has a shitload of O2. So basically, if you overwater, you stop air from getting to the roots.