To be fair, hippos are very scary: they kill around 3000 people in a year, and those jaws that they have are no joke (yes, hippos are strong despite what their chunky look shows to you). Now, a hippo that creates sandstorms out of nowhere? Talk about a buff.
No wonder why Drapion's scared of Hippowdon: being weak to ground types doesn't helps at all while fighting a hippo that can create sandstorms and has enough power to crush its foes.
NGL, I would be scared of it too.