Something that I think contributed to the higher finisher rate was the selection process. The ASO as more entries than space available, and so have been selective in who they'll let in. Elite rider, then past finishers, then past competitors, then the others vetted on who has a 'pedigree'. So: better riders, more capable of finishing.
Then you have the bikes. Most run a 450RR, a well proven mount capable of completing without drama. So: Better (more reliable) bikes.
It looks to me that the regional politics play a big part in South America, dictating the routes and destinations. Couple that with areas that are just plain impassable. They cover damn near a quarter of that continent, there's gonna be a lot of distanced covered if you just rode from Lima to Santiago, let alone throwing in another country detour.
I do think the finishing stage and finish line ceremonies were in bad taste. Special guests only? Elite viewing? That would royally piss me off if they did it here, to see this sort of thing going on with Dakar kinda flies in the face of every non-elite racer.
To me, I know it had the effect of not liking Chile much, and wouldn't be interested in spending any of my time or money there. Read enough ride reports to realize that your average joe there is quite friendly, but be damned if I'm giving that gubmint any money if that's the way they treat their own in a public forum.
Makes you wonder how they treat them out of the light of day.
South hombre, the setting sun to the right until we are out gas, cash or goddamn snow.