Former Irish international Donal Lenihan said O'Gara, who had two seasons as an assistant coach in Super Rugby with the Crusaders before taking up his appointment with La Rochelle, had lifted what was an already impressive coaching career to an all-time high with his Cup success.
Lenihan wrote in the Irish Examiner that O'Gara devised a master play to deny Leinster the time and space they like to take teams apart.
Leinster had 13 Test players from the recent Six Nations who were 'playing with a fluidity and understanding rarely achieved by even the best of club sides'. The final was Leinster's to lose, he said.
"The fact that they performed nowhere near their best, on the biggest day of the season, can be attributed exclusively to the desire, guts and willingness of a desperate La Rochelle squad to play to the death even with the odds stacked against them."
O'Gara also showed how much he had learned from his Crusaders' experience, Lenihan said.
"Facing a side of Leinster's quality, the last thing O'Gara needed was losing two of his team's standard-bearers in All Blacks Victor Vito and Tawera Kerr-Barlow to injury in the period leading into this contest.
"By his own admission, one of the biggest lessons absorbed from his time in New Zealand with inspirational Crusaders head coach Scott Robertson was to back the qualities of the next man promoted due to injury, to build his confidence and let him loose," he said.
The players concerned had been big contributors to Saturday's win.
Lenihan said O'Gara targeted former Blues halfback Jamison Gibson-Park to deny him the time to give his backline the start they preferred. That was through attacking the breakdown in the loose and applying pressure through the scrum to force quick strikes to deny Leinster the time to launch the clever plays they liked from the set-piece.
Lenihan warned that the consequences of the loss would not apply only to Leinster.
"The implications of this defeat will have extended all the way to New Zealand where the All Black coaching team are currently devising a template for the forthcoming Test series against Ireland.
"Unfortunately, Leinster may not be the only ones to suffer on the back of this loss," Lenihan said.