@selzero
Hippos can run faster than you on land, swim faster than you in the water, and are big enough that they can just run you over and kill you, but they don't do that, they gore with their tusks and slam with their heads. Their bite is strong enough to break a crocodile in half, and even though they are herbivores they are opportunistic carnivores and even cannibals. They're territorial and have unpleasant temperaments with pretty much anything but their young, which is why the ancient Egyptians used a personification of a hippo as their goddess of childbirth and fertility. The Egyptian name for the goddess was Tewaret, which translates literally to "she who is great" because even the hippo god was dangerous enough that you didn't mess with her.
Part of the reason why hippos kill so many people is that tourists think they're docile and behave stupidly around them when they should be given an extremely wide berth. But hippos also just capsize boats and drown/maul people who never saw them coming. Fishermen are common victims. That doesn't mean you're safe from hippos on land though. Far from it. They are territorial about the land surrounding their water territory as well. Basically, if you're close enough to a hippo's territory, you're in incredible danger.
All that said, some sources I've seen say that crocodiles kill more people than hippos, but there aren't reliable numbers to prove it either way. The number quoted in your meme is on the high end; most sources say hippos kill about 500 people a year, which is still pretty impressive for an animal that doesn't come into contact with that many humans.