He probably had facial recognition turned on so all the FBI had to do was point the phone at him to unlock it. If he had just used a six-digit passcode, they would not have been able to open his phone.
Once they got into his phone, his cloud storage was compromised, too.
The country is really circling the drain with these Gestapo / totalitarian tactics becoming a daily occurrence. It is very frightening.
Banana Republic here we come.