From MSNBC about the upcoming sentencing hearing:

Judge Merchan’s critics had two main questions: Wouldn’t this punishment amount to a slap on the wrist, undermining the rule of law? And why couldn’t the judge wait and leave the sentencing hanging over Trump’s head until after he left office in four years, when his presidential immunity no longer applied?

It’s not the usual situation a judge finds himself in when sentencing a convicted defendant. But the Supreme Court gave Trump immunity no one else possesses: broad immunity from criminal prosecution for a president’s official acts. The criminal conduct in the Manhattan case occurred before Trump became president and was clearly personal, not presidential, conduct. Trump used the Supreme Court’s ruling last year to delay his sentencing date to a point so close to the inauguration that a sentence including incarceration was no longer a realistic possibility.

But something more important than the sentence is at stake here: the conviction. Judge Merchan underlined the importance of the jury’s decision in his order. “The significance of the fact that the verdict was handed down by a unanimous jury of 12 of Defendant’s peers, after trial, cannot possibly be overstated,” he wrote. “Indeed, the sanctity of a jury verdict and the deference that must be accorded to it, is a bedrock principle in our nation’s jurisprudence.”

A couple of paragraphs later it explains how to avoid Trump wiping the slate of these convictions:

The key to making sure Trump can’t wipe out the jury’s verdict is completing the appellate process. The conviction isn’t final until then. The clock for the appeal starts once sentencing is complete. Once Trump is sentenced, he has 30 days to file. If Judge Merchan had put off sentencing until 2029, Trump's conviction would not be on the path to becoming final.

The article is Trump asks Supreme Court to stay his sentencing. Judge Merchan was right. They have a paywall but when it pops up I open the article with the Just Read browser extension (in Chrome or Firefox) to read it.