The U’s owner came under more scrutiny than at any other time during the eight-week period after Wilder’s exit in January.
It ended with Waddock being named as head coach last month and Lenagan believes he has never been more enthusiastic at United.
“It’s higher at the moment than it’s ever been, because I’ve gone through the terrible period of changing a manager,” he said.
“That’s not a nice thing to go through. It’s a terribly telling time and it knocks chunks off you doing that.”
Waddock claimed his first win with a 2-0 success at Plymouth Argyle last weekend, which saw United go back into the play-off places in Sky Bet League Two.
Although it came after three successive defeats, Lenagan has been impressed with the impact the former Wycombe boss has made behind the scenes and the pair have been busy this week preparing for next season.
He said: “At the end of Saturday I was utterly delighted with where we are with Oxford.
“I’ve spent the last three days on Oxford business and loved it completely, planning the squad for next year – I’ve spent hours with Gary.
“There’s nothing better than planning for a new season, particularly where you can plan around a football philosophy that you believe in.
“I believe completely in the football philosophy of Gary Waddock.”