At the same time he violated laws meant to protect investor from losses. But if they didn't actually lose something, it would make sense to have a modest sentence. Not knowing what his reckless behavior actually caused would make the sentencing frivolous in my opinion.
That's not how it works. "No one got hurt" is a facile exoneration, and untrue at that. He didn't break the law "less" because by twist of fortune money showed up in the account sometime down the line.
Loss causation is described here [1] as the major factor influencing the sentencing range, so if all investors are made whole then a modest sentencing could be possible. It was also discussed in a recent Matt Levine newsletter.
Especially when a lot of the "lack of loss" is due to the speculatory appreciation of cryptos as a whole, not due to anything on SBF's behalf. If crypto had crashed, they could equally be looking at almost nothing.