CZ was not convicted of fraud or even money laundering. There's a reason the sentence was only 4 months. His charge was the first ever prosecution of a platform/bank poorly implementing KYC and not doing enough surveillance of its users to comply with the letter of AML regulations. The case relied on the theoretical possibility of US citizen users placing trades that are matched by people from sanctioned countries - it did not even find cases of such trades. Big banks routinely pay fines for this, and never face imprisonment.

Regardless of what you think of the circumstances of the pardon, the prosecution was not related to fraud and was an unusual case by a DOJ that was recently embarrassed by FTX and was arguably symbolic in intent.