“WASHINGTON (AP) — The FBI obtained a secret court order last summer to monitor the communications of Carter Page, an adviser to then-candidate Donald Trump, because the government had reason to believe Page was acting as a Russian agent”
It looks like any reason was good enough to spy on US citizens. The FISA court did not reject one request in 6 years.
FISA: 9,400 to Zero | During Obama Admin. Spy Court Denied No Electronic Surveillance Applications