Don’t forget we’ve put more people into space than have been to the deepest point on the planet.
Fun fact, space is easier. It takes more effort to get there, sure. Coming from the “normal pressure” here on earth (about 1 atm) and going to space (0 atm) is a pressure difference of 1 atm. But: Diving into the ocean, the pressure increases the deeper you go. For every ~10 meters (~33ft) you go deeper, the pressure increases by 1 atm.
That means, that a space ships would only need to dive 10 m deep to get to the pressure difference it experiences in space. They went to see the Titanic which is about 3,800 m deep. So the sub needs to withhold a pressure difference that’s about 380 times higher than a space ship experiences.
(OK, little difference I omitted: In space you need to prevent the vehicle from exploding, while in the deep sea you need to prevent it from imploding)