Why is Trump so desperate to protect Flynn?

Trump has desperately tried to protect Flynn. Trump was warned multiple times, by Obama, by multiple intelligence agencies, by the Acting Attorney General, that Flynn was working for Russian interests, taking Russian money and was vulnerable to Russian blackmail.

But Trump asked the FBI to drop the investigation of Flynn, he asked the Defense Intelligence Agency to pressure Comey to drop the investigation, he asked Congressmen to stop the investigation of Flynn. And Trump finally fired Comey in the mistaken idea that this would stop the investigation into Flynn.

Why was Trump so desperate to protect Flynn, and why did he hire him in the first place? Court documents filed recently prove that Flynn was working under the direction of the White House. And in the White House, there were only two people over Flynn: Kushner, or Trump himself.