Nuclear power plants were designed with this in mind. It would take a substantially larger earthquake to damage a nuclear power plant and cause it to leak than a commercial pool. Such a comparison is in bad faith and disingenuous.
People are fallible on the best days, assuming everyone did their very best from nuclear physicists to construction workers, mistakes are made. You take steps to reduce the risk. Research gets review. Engineering schematics get review. Construction gets inspection. Still some mistakes will get through.
And people always act their very best all the time right?
You can even have a perfect design, perfect construction, that is mismanaged years after it's built, after the original engineers and bureaucrats lose control.
The same people problems apply to basically every human endeavor, but nuclear's capability to cause accidents that have a lasting impact is pretty scary. You don't feel even a twinge of existential dread when you think about? If you don't, then I don't think I want you working on a reactor.
Unless we plan on getting the pope to build nuclear power plants, which does sound cool.
If our smallest manmade lakes (swimming pools) can leak a lot, and our largest manmade lakes (dams) can also leak a lot the idea there's an in-between size that doesn't leak might need a bit of elaboration.
The safety requirement here is not "doesn't leak", it's "holds most of the water for 30 days (after which water is not required)". You would have to get an implausibly-large leak, during a situation where nobody can add more water for a month.
There are pools and pools and there are leaks and leaks. Anybody that has built an aquarium knows that a 80cm high design is much more complicated to made leak-proof than a 40cm high design holding the same water.
A shallow pool would not be enough to contain a small nuclear plant, so you need a non standard bigger pool. Higher the pool, higher the weight of water column, the force pressure against the walls will increase, and the leak will be much faster because the water weight in the upper level of the pool will force the water in the low levels to go out. If your leak is in the upper side of the pool will be a small self contained problem but if the bottom leaks is a different thing. As the bottom needs to support much more force against it and there is a weak area when walls meet bottom, is more probable to fail first.
"Substantially larger" is not the same as "impossible". And, given substantially larger consequences if a reactor pool breaks (compared to a swimming pool breaking), I don't think the question is out of line.
We learned from Fukushima that natural disasters don't always follow the parameters that we expect them to.