Max Verstappen spearheaded a Red Bull one-two on Ferrari's home turf on a day when he also rubbed salt into Lewis Hamilton's gaping wounds.
The reigning F1 champion was never threatened in the Emilia Romagna Grand Prix once he pulled away cleanly at the start in wet conditions, going on to cruise to the 22nd win of his career.
After clinching the point for the fastest lap at Imola, it means Verstappen is now just 27 points behind Leclerc who suffered a late spin whilst chasing Sergio Perez for second, leading to him crossing the line sixth.
For Red Bull, it was a day long overdue as the Milton Keynes-based team scored its first one-two since the 2016 Malaysian GP, with McLaren's Lando Norris third.
As for seven-time champion Lewis Hamilton, the culmination of one of the worst weekends of his career resulted in him finishing a wretched 13th as he was unable to make any progress, and even worse, he was lapped by Verstappen at one stage.
For only the third time in his career with Mercedes, with the obvious exception of retirements, Hamilton was classified outside of the top 10 in taking the chequered flag.
Rain leads to wet start
Following heavy rain from late morning through to early afternoon that finally stopped around two hours prior to the start, it meant all cars were on intermediate tyres once the five red lights disappeared.
Unlike at the start of the sprint on Saturday, from top spot on the grid, Verstappen made the ideal getaway and instead it was Leclerc who got bogged down as both Perez and Norris made their way past on the run down to the first chicane.
Behind that leading quarter, the second Ferrari and McLaren of Carlos Sainz and Daniel Ricciardo tangled, with the Spaniard ending up in the gravel where he again beached his car for the second successive race.
On this occasion, unlike in Australia where the fault was totally with Sainz for his lap two exit, the Spanish driver was hit by Ricciardo as the pair tried to go through the chicane side by side.
With no escape for Sainz, while Ricciardo at least managed to make his way back on track, albeit falling to the back of the pack, an inevitable safety car was summoned to allow the stricken F1-75 to be removed.
After a three-lap hiatus behind the safety car, Verstappen soon extended his lead to Perez, while Leclerc moved up to third with a move on Norris on lap eight.
Alonso exits as teams make slicks switch
Shortly prior to that Alpine's Fernando Alonso had become the second retiree due to a major hole appearing in the sidepod of his Alpine.
That was as a result of bodywork being ripped from his car at speed following a collision with Haas' Mick Schumacher coming out of Tamburello on lap one.
From lap 18 onwards with a dry line emerging on the track, but with teams reporting the threat of more rain, Ricciardo was the first to gamble by taking on the medium tyre.
It sparked a flurry of stops, surprisingly with Verstappen one of the last to do so but with enough of a cushion beforehand to ensure he was never troubled.
Leclerc at least managed to jump Perez, but after stopping a lap earlier and with heat in his tyres, the Mexican soon made short work of the Monégasque to reclaim second.
Further back, Hamilton suffered further woe as he lost two places, dropping from 12th to 14th, albeit with one of those due to an unsafe release from Alpine with Esteban Ocon.
The seven-time champion was forced to brake hard to avoid colliding with the pit lane wall, leading to a five-second time penalty for the Frenchman.
Ricciardo goes long as Hamilton suffers blue-flag embarrassment
After 31 laps of the 63, McLaren brought in 15th-placed Ricciardo, who had caught up to Hamilton, and switched him onto the hard tyre in a bid to see out the race.
At that stage, the race had become static, primarily due to a woeful lack of overtaking as DRS was not enabled until the start of lap 34.
Even then, Hamilton was unable to find a way past AlphaTauri's Pierre Gasly ahead of him, and then came the ultimate ignominy.
With leader Verstappen on his tail, the Briton was blue-flagged, embarrassingly giving way just as the duo crossed the line at the start of lap 41.
Leclerc suffers shock spin
At a point when Leclerc was pushing Perez for second place, he hit the kerb hard on the entry into the Variante Alta and unable to control his car to take the exit, he was sent into a spin, hitting a barrier with the left-hand side of his car.
Leclerc was able to continue but immediately ventured back into the pits for a new set of softs, dropping him down to ninth.
The 24-year-old at least made up three places by the flag to claim sixth, with George Russell in his Mercedes and Alfa Romeo's Valtteri Bottas ahead of him.
AlphaTauri's Yuki Tsunoda, Sebastian Vettel in his Aston Martin, Kevin Magnussen for Haas and Lance Stroll in the second Aston Martin completed the top 10.
Hamilton crossed the line a demoralising 14th but was elevated a position due to Ocon's time penalty.