It's about deterrence. Imagine you're considering committing a crime. You're looking at the upside and the downside. The equation on the downside looks like this:
risk = size of punishment * probability of being caught.
So how do you deter a potential criminal who is unlikely to get caught? You have to jack up the size of the punishment to compensate for that low probability.
In other words he's not being punished for what he did; he's being punished to dissuade others from copying him. I think people should be punished for their actions and not to increase utility of society.
FWIW, I've read that multiple people committed suicide in despair of the financial ruin caused by SBF's fraud. So he did do things worthy of hefty punishment.
Stealing money may not inherently "feel" like a real crime, because money (especially digital crypto money) is a very intangible hypothetical thing. It does not resonate with our lizard brains like violence does.
However, it is a real crime. And harsh punishments like prison time are needed to remind us of that.
risk = size of punishment * probability of being caught.
So how do you deter a potential criminal who is unlikely to get caught? You have to jack up the size of the punishment to compensate for that low probability.
Economist Gary Becker started this school of thought in the 60s and it's been implemented and debated in a million ways since then. Example: https://masonlec.org/site/rte_uploads/files/JEP/Readings/But...