For former President Donald Trump, showing up in New York for the start of his civil trial Monday was more than a political stop to boost his 2024 campaign. It was also deeply personal.

Several sources who spoke with CNN said Trump's decision to attend the hearing after the judge found Trump had committed fraud by inflating his riches was largely driven by how the accusations strike at what Trump values the most: his business and his brand.

"They're hitting him where it hurts," one of the sources said, noting that Trump was publicly seething as he entered and exited the courtroom Monday, stopping to speak with reporters on multiple occasions.

Trump has been fuming in recent days since the judge issued the surprise pretrial ruling last week. He has vented the most about the proposed valuation of his bedrock property in Florida, the Mar-a-Lago beach club. Trump was incensed after the judge used an $18 million to about $28 million assessment for the actual value of the compound.

While in Manhattan, Trump repeatedly and brazenly attacked New York Attorney General Letitia James, who launched the case and was in the courtroom Monday, as well as the judge overseeing it, Arthur Engoron. While the public broadsides were against the advice of his attorneys, Trump has dismissed pleas to tone down the rhetoric.

He has instead told those closest to him that he doesn't care if any of the judges in his multiple cases seek to punish him, arguing it will benefit him politically if they do.

On Monday, he sought to tie James and Engoron to special counsel Jack Smith's criminal indictments of him, even though they are unconnected.

"This has to do with election interference, plain and simple," Trump said before walking into the courtroom. "They're trying to damage me, so I don't do as well as I'm doing in the election."

Trump, leaving the courtroom on a lunch break and approaching cameras in the hallway, railed against what he had heard, attacking the judge as an "operative," and said he should be disbarred for ruling against him.

Asked why he showed up in person Monday, Trump issued a familiar refrain: "Because I want to watch this witch hunt myself."

The former president, at the end of the day, complained that he had been kept from the campaign trail -- even though he was there voluntarily.