"Well, it was very tough, I'll tell you," Bryan told ET's Lauren Zima, as he opened up alongside fellow judges Lionel Richie and Katy Perry. "I learned how much I loved the investment that obviously me and Lionel and Katy have put in [to the season]."
"I mean, it was really, really tough not being there. That was the toughest part of quarantine," Bryan said. "It was really tough for me to have to miss out but I was really honored and very amazed that Paula stepped in for me."
After testing positive for COVID-19, Bryan returned to his family's home in Tennessee, and stayed largely isolated, relying on his wife, Caroline Boyer, for help during his quarantine.
"I put myself in a part of the house and stayed away from my boys," Bryan explained. "I really didn't want the boys to miss any school so [one of the hardest things was] not being able to hug all my children."
Perry and Richie spoke with ET after last Monday's show, and the pair revealed that Bryan had been texting them from home while watching the show live on TV, to give them feedback in real time.
"It was really interesting to talk to Lionel and Katy and really tell them how wonderful some contestants looked on TV," Bryan explained. "Even in the room, we miss out on some of the nuances of pitchiness and vocal stuff, but when you're on TV, the TV doesn't lie. So I could kind of tell Lionel and Katy some stuff."
During Sunday's show, the Top 12 was whittled down to just nine. After all the songs were performed, and America had a chance to vote, the Idol journey came to an end for Ava August, Madison Watkins and Beane.
Meanwhile, Alyssa Wray, Caleb Kennedy, Casey Bishop, Cassandra Coleman, Chayce Beckham, Deshawn Goncalves, Grace Kinstler, Hunter Metts and Willie Spence will all be moving on to perform in the next round.
Monday marked a big night for Bryan even after his return to Idol. Later in the evening, the Born Here Live Here Die Here artist also won the Entertainer of the Year Award at the 2021 ACM Awards, and accepted the honor virtually -- as the show took place in Nashville while he was in Los Angeles.
American Idol airs Sundays and Mondays at 8 p.m. ET/PT on ABC.