Martin O'Neill needed a win after his recent travails and this was a stroll in the park that he could not have imagined.
Football management can be a horribly stressful business that can put years on you. After this, O'Neill looked younger not older. The ageing process worked in reverse thanks to his team feasting on Hearts' scarcely believable weaknesses.
The stats are, frankly, hilarious. If it was a horrific day for Wouter Vrancken and his players then it was every bit as grim an experience for those who try to see sense in numbers.
Hearts had more shots than Celtic (20-18). They had more shots inside the box (16-13). They had more possession (52%-48%). They had more crosses (16-10). They won more duels (51%-49%). They had more passes in their opponents' half (244-202). They had more accurate passes (458-423).
That last one was laugh-out-loud funny, for Hearts' use of the ball was comically bad.
So often, when under a little bit of pressure, or no pressure at all, they passed into space only for Celtic to gobble up the loose ball and launch an attack which usually ended in a big chance or a goal.
The home team was slick. Benjamin Nygren, Callum Osmand, Camilo Duran and Haissem Hassan were devastating. Seven did not flatter them in the slightest.
It began with those two early goals - Liam Scales showing the desire to win a near-post header from a corner and Kieran Tierney left alone a few yards out to force in, then Dane Murray outfighting Claudio Braga to help it back to Nygren to score.
Hassan hit a post when he turned and darted away from Stephen Kingsley. People wondered what was Vrancken going to do to change this. Answer: nothing.
When Celtic score seven it seems odd to talk about pieces of defending they did that were significant, but Colby Donovan's cameos warrant mention.
Around the midpoint of the first half, Hearts stirred a little. You wouldn't say that they had momentum, but they had a bit of a possession and their hair-on-fire panic of the early minutes seemed under control.
Twice in the space of three minutes, Josh McPake - one of the form players in the country - took on Donovan and twice Donovan routed him.
Those little duels might disappear from relevance after the deluge, but at the time they were important. The Hearts dangerman had been snuffed out. His morale had taken a hiding. And the stadium loved it.
Hearts fell apart at the seams from there. Sabri Guendouz gave the ball away and Duran combined with the impressive Osmand to score number three.
Jamie McCart then became detached from his trolley and Celtic scored from that error, too. Osmand, again, but with lovely work from Duran. And easy, oh so easy.
Celtic's pace in attack was terrific. Their alertness was outstanding. Their disbelief was there, too. How could a team with a seemingly good coach and a strong squad of players be performing like a pub team?
Hearts fans started heading home at that point. They missed the goal that made it 4-1. They won't have shed any tears. Had they gone back they'd only have suffered on. Best get out of dodge as quickly as possible.
Soon, it was 5-1, Mika Baur slaloming his way past the comatose figures of McPake and Malachi Fagan-Walcott to dink a shot on goal, helped on its way by Kingsley and McCart, sitting on the floor, all flailing legs, like an octopus who had fallen out of a tree.
Hearts' heads had long since gone. They were a broken team, psychologically. The doubt and fear coursed through their veins.
The easiest things became difficult. The difficult things became impossible. They had no discipline, no direction.
Vrancken spoke later about individual errors and that was obvious, but what else? He was given an opportunity to take some responsibility for the way he set his team up to begin with, but he declined to go there.
On reflection, maybe he will. He should. Gung-ho football is fine when it works. Unless it's laced with some pragmatism when facing the best teams in their own backyard then it can blow up in your face, which it did at Celtic Park.
Then it was 6-1 (Laurent Mendy the culprit, followed by McCart) and 7-1 (Tomas Magnusson in the frame). Duran and Nygren finished with aplomb. Seven minutes remained. The expectation was that this could still become eight or nine.
We like to think this league title race can be a three-horse thing again this season. We want the drama of last time.
Hearts played Celtic four times last term. They won two, drew one and lost one. They had nous and resilience before it all slowly slipped away from them.
This team has talent but, with their away record as it is, they're not going the distance, or anything close to the distance.
Celtic will be buoyed by this. Using it as fuel is the next step.
Osmand was a big player for them. O'Neill might have hit on a powerful front three that doesn't involve Kasper Hogh from the start.
After some rough days and nights they have some of their feelgood back. Keeping it on the long road ahead is the challenge now.