Because he has a lot too hide.
Trump is furious after House Intelligence Committee Chairman Adam Schiff hires former NSC aides to help oversee the Trump's administration.
Rep. Devin Nunes, the former Republican chairman of the committee, hired former National Security Council Middle East director Derek Harvey after he was dismissed by then-national security adviser H.R. McMaster.
Trump has a long financial history with Russia. As summarized by Jonathan Chait in an invaluable New York magazine article: “From 2003 to 2017, people from the former USSR made 86 all-cash purchases — a red flag of potential money laundering — of Trump properties, totaling $109 million. In 2010, the private-wealth division of Deutsche Bank also loaned him hundreds of millions of dollars during the same period it was laundering billions in Russian money.
‘Russians make up a pretty disproportionate cross-section of a lot of our assets,’ said Donald Jr. in 2008. ‘We don’t rely on American banks. We have all the funding we need out of Russia,’ boasted Eric Trump in 2014.” According to Trump attorney Michael Cohen’s guilty plea of lying to Congress, Trump was even pursuing his dream of building a Trump Tower during the 2016 campaign with the help of a Vladimir Putin aide. These are the kind of financial entanglements that intelligence services such as the FSB typically use to ensnare foreigners, and they could leave Trump vulnerable to blackmail.