We shouldn't have been surprised.
In fact, plenty of Australian football fans will say they foresaw this success for Ange Postecoglou, even if the rest of the footballing world barely disguised their lack of faith.
And yet, Postecoglou has silenced those European sceptics to lead Celtic to a thoroughly deserved Scottish Premiership title at the first time of asking, clinching the title with a 1-1 draw away to Dundee United.
Twelve months ago even the hardiest of Celtic fans would have had a hard time believing this was possible.
Celtic were at a low ebb, without a manager and facing a resurgent Rangers that had comprehensively ended their tilt at a tenth successive title, beating Celtic into second by 25 points.
Bitter rivals Rangers, under Steven Gerrard, won that year's Premiership with a whopping six games to go — the earliest a side has ever won the league.
It was the first season since 2009/10 that Celtic had failed to win a trophy.
Players were leaving, the fans were off side and their biggest rivals were on the up: hardly a good time for an enigmatic and underrated coach from Australia to take charge of one of Europe's biggest clubs, one would think.
And yet for Postecoglou, perhaps it was.
After all, his style demands total buy in, a sea change in belief and style that can only come when a club is, perhaps open to change.
That's what happened in Brisbane with the Roar, which required a wholesale clear out of some of Australian football's biggest names to create a team nicknamed Roarcelona such was their attractive style of play.
It happened with Australia too, after the Socceroos had been hammered 6-0 by both Brazil and France in successive matches prior to him taking charge. He led the Socceroos to Asian Cup success in 2015 and World Cup qualification in 2018.
It was also the case at Yokahama with an F.Marinos side that had not won a title in 15 years prior to being blessed by the presence of Postecoglou.
In Japan, Postecolgou was given time, finishing 12th in his first season before his methods and philosophy permeated through a near-impregnable language barrier to create the free-flowing style that earned them the J-League title the following year.
At Celtic, time is not a luxury afforded to anyone.
"This isn't a club that should go years without any trophies," Postecoglou told the BBC after winning this year's League Cup with Celtic, ending a brief trophy drought.
"My first task when I took the role was to give the fans hope.
He couldn't guarantee success, but he sure has delivered it, overhauling a cavernous points deficit to Rangers from the previous year to fly past and win with a game to spare.
Managing Celtic was a challenge unlike anything Postecoglou had ever faced in his extensive, 26-year managerial career to date.
Such is the relative strength of Glasgow's Old Firm, matches between the pair are what count, with the rest of the 12-team league expected to be swatted aside with ease.
Every club hopes for success. Few demand it.
Rangers and Celtic, the two enormous fish in the ever-shrinking Scottish Premiership pond, are expected to win the title every year — Celtic have not finished any lower than second in the league in 27 years.
In Old Firm matches this season, honours have been even: Five games in league and cup, two wins apiece and a draw the result.
It's in the matches that Celtic have been expected to win that they have bettered Rangers, who struggled in January and February having lost manager Gerrard in November.
That's not always been the case with Postecoglou teams due to his adherence to a set style of play with a view to continually develop, rather than eke out wins by any means necessary.
That philosophical rigidity only impacted Celtic at the start of the year, when Celtic took just two wins and a draw from eight matches to sit sixth on the ladder.
The doubters sharpened their pitchforks, but the squad, bolstered by 14 new signings, were starting to gel and the free-flowing style for which Postecoglou has become synonymous was proving far too much for Scotland's lesser lights.
Those new signings have also proved to be a masterstroke by Postecoglou.
Six Celtic players were named in the Professional Footballers Association SPL team of the year. Four of them: Cameron Carters-Vickers, Josip Juranović, Jota and Kyogo Furuhashi, were signed by Postecoglou.
Kyogo is the most interesting of those signings given he is one of four J-League players that followed Postecoglou from Japan to Europe — moves that raised eyebrows when they were announced.
Postecoglou was greeted with heaps of scorn from the British press who cared little about his impressive record in leagues outside the limelight.
Former Scotland striker Alan Brazil became something of the face of Scottish football's ignorance with his now infamous TalkSport segment.
Rangers legend Ally McCoist, who laughed along with Brazil as he incredulously asked whether Postecoglou's naming as Celtic boss was a "wind up", has since eaten his words.
"He's done a great job there and has continued to do a great job," the Rangers legend told Sky Sports after Celtic's League Cup win earlier this year.
But success at Celtic does not mean winning one Premiership, not by a long shot.
If he wants become a legend at Parkhead, he'll need to win next year too. And the year after. And the year after that, with a smattering of cup successes and lengthy European Cup runs thrown in for good measure.
Getting on top is almost the easy part of life at one of the Old Firm. Staying there is something else entirely.
However, now he's shown his tactical wares in the crucible of Scottish football, Postecoglou will be a marked man for those who lead the big clubs south of the border.
There is little doubt that the first managerial casualty of the 2022/23 Premier League season will lead to calls for Postecoglou's style to be blooded in England, particularly if he can lead Celtic deep in the Champions League, as big an ask as that is for a team with a fraction of the budget of the erstwhile Super League wannabes.
That will be a different, bigger test again, particularly with financial inequality making measures of success so varied across the league.
Would it be unwise to jump straight into that shark pit, as Gerrard has done with Aston Villa and former Celtic man Brendan Rodgers did at Leicester?
Perhaps, but there is little doubt that if Postecoglou does opt to go down that route, or is at least given the chance, he will succeed.
Because that's what he does and what he continues to do, everywhere he goes.
