Speaking to the Panthers before their team song on Sunday night, Cleary praised their resilience after a 14-6 triumph over Melbourne which capped a defensive masterclass in the finals.
The Panthers' premiership came despite halfback Nathan Cleary playing only 10 regular-season games, while Dylan Edwards, Liam Martin and Scott Sorensen also battled injuries.
"It's probably a bit of everything," coach Cleary told AAP, explaining why this was his side's best title.
"The style of game, the way we played in the finals after we didn't really come into the finals playing that well.
"Playing against Melbourne, who are just peerless in the last 20 years of the NRL. They have had a great year. All their best players are in good form.
"All that together, and just the way the game went ... It's unbelievable."
Penrith players labelled Sunday night's win as physically the toughest of their four successive grand final victories.
Their 2021 win over South Sydney had a thrilling finish, 2022 against Parramatta was a domination and 2023 featured the greatest grand-final comeback against Brisbane.
But Sunday's win was their grittiest in the middle, as the Panthers suffocated Melbourne out of the game and rarely offered the Storm's attacking weapons any good ball.
The effort continued a remarkable run in finals matches, with Penrith having won a record 12 on the trot while conceding only 9.3 points per game since the first of those matches in 2021.
This year's finals also came after Cleary publicly challenged his team's hunger in the lead up, after the club's post-Origin form slump and his son Nathan's shoulder injury.
"There were definitely times this year where I could see little pieces of complacency," Cleary said.
"Whether it was during games or before certain games they just weren't as consistent or ruthless as we would like to be.
"Even finishing the year, we weren't anywhere near where we needed to be. That's why I made the comment I did. I wasn't trying to put them on the spot, it was just honesty.
"It's probably human nature. A lot of our guys, the amount of football they have played over the past five years. This year's Origin series took a lot out of them.
"But when we hit the finals we clicked into gear. Our defence was back. It was easily the best it has been this year through the finals."
Cleary remains adamant that hunger can return again next year, as the Panthers hunt a quintet of premierships without Jarome Luai, James Fisher-Harris and Sunia Turuva.
"We'll have a new group again, we've got some challenges for sure with guys leaving. But we've done it before," Cleary said.
"I'll know when they all turn up how they're looking. I know what they're like. I think they'll be alright."
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