Andrew Arrabaca, 43, was armed with two axes, a machete, three knives and fireworks, says the FBI.
Thousands of people attended the event last month, including President Trump and Vice-President JD Vance.
The longtime Google employee was charged in New York for allegedly breaking insider trading laws.
Agents also found about $2m in cash and 35 luxury watches in the home of David Rush, who court filings say had top secret clearance.
The rural house sheltered Daniel Andreas San Diego, who evaded the FBI for 21 years.
Prosecutors say a 2025 seashell photo posted by the former FBI director was a call for violence against Trump.
Patel alleges that the magazine published false and harmful claims about his conduct, including accusations of excessive drinking and unexplained absences from duty.
Prior to the attack, the suspect searched online for pro-Hezbollah news channels and for large gatherings of Israelis in Michigan, the FBI said on Monday.
A hacker group shares Patel's purported resume and photos - information, the FBI says, is "historical in nature".
