Jackett resigned on Tuesday after six-and-a-half years at The Den, saying he felt it was time for a new challenge.
Palace had battled to a goalless draw with Millwall seven days earlier and Holloway admitted he had no idea Jackett was thinking of leaving.
"I had a drink with him after the game on the Tuesday night and there was no indication he was feeling like that at all," said Holloway.
"But he was the longest-standing manager and the atmosphere down there, worrying they might go down, was really tense.
"Maybe he feels he needs a change. It's been nearly seven years in one place and after getting to the semi-final of the FA Cup, maybe he's had enough.
"But looking back at his time there no-one could deny how well he has done."