Heavy rain had moved into the previously icy and snowy region as the cars were in the mid-evening service, and as the worsening conditions prompted hordes of spectators to leave the stages, local roads became badly congested.
The situation ultimately reached the point where the organisers felt compelled to cancel stages 17 and 18 as the level of traffic would have made it impossible to put their action plan into place in the event of an incident.
Results will therefore be taken from the end of SS16, with Loeb winning for Citroen ahead of Volkswagen's Sebastien Ogier.
The other two works Citroens of Dani Sordo and Mikko Hirvonen finished third and fourth.
Loeb controlled the event for most of the week, although Ogier had initially sprung a surprise by setting the stage one pace.
There was generally little to choose between Ogier and Loeb, but the champion made a crucial break when he pulled a minute clear on Wednesday afternoon.
Not that anyone knew how far ahead Loeb was for a while, as that loop saw major problems with the new SIT timing system and several hours of confusion before correct results could be obtained.
Once Loeb had escaped, Ogier was content to settle for second, insisting there was no need to try and beat his former team-mate as he would not be a title threat.
Ogier was the only VW at the finish, with team-mate Jari-Matti Latvala crashing from sixth on the final day.
Citroen had plenty to celebrate with Sordo third, albeit nearly four minutes behind Loeb, and Hirvonen fourth despite some confidence dips.
Bryan Bouffier took his PH Citroen to fifth on his World Rally Car debut, despite several minutes off the road on Friday.
It was a week of promise and disappointment for Qatar M-Sport. All their Fords flew at times, and Evgeny Novikov was battling Sordo for a podium.
Novikov's challenge ended when he crashed at the start of the final leg, just as team-mate Juho Hanninen would later on the same stage.
With Thierry Neuville having gone off on day one while running fourth, M-Sport's only points came from Mads Ostberg's sixth place. The Norwegian survived electrical problems on day one and suspension damage on Saturday to complete his maiden Monte.
The level of attrition meant Sepp Wiegand took eighth overall as he won the new WRC2 class, which he dominated after rapid Skoda team-mate Esapekka Lappi's early exit.
WRC3's debut featured only two entrants and one finisher: Citroen protege Sebastien Chardonnet.
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