You'd think Nissan would have their shit together now, given their resources.
To be fair they tried something radical and it *could* have worked if it didn't get caught in a chain reaction of problems.
Ignoring the oddball choice of a mostly FF car.
The hybrid system didn't work, this meant they were down to about half power and that all of that power was coming through the front wheels when some was supposed to be delivered by the rear as well (about 200bhp out of the 1250+). They had to carry that hybrid system around even though it didn't work which is a couple of hundred kilos of dead weight. With no hybrid system to absorb the energy under braking they had to fit different untested brakes and even then they overheated. With the different brakes they had to fit different wheels and tyres, bits that were *really* not designed for the car. From all of this and the lack of testing they were running the wrong suspension system and set-up producing a car that was absolutely horrific over kerbs and on tight locks.
It wasn't all a failure, thanks to the cars fancy super slick aero and body tunnels it was the 2nd fastest car on the straights despite only having half power and to be honest if fully developed could have been a top tier runner at LeMans.
But that brings us to another problem, the WEC. It isn't only LeMans anymore, with 6h races scattered across the globe and every one of them being 1:An awesome race and 2:An awesome test session you can't have a car that only works at one event anymore, even if it is 'the big one'.
It was a PR disaster for Nissan, one that gave them cold feet about the event which they had publicised heavily so it was either come back and dominate or quit. They went back to testing and from various sources that testing was going well and the car was visually evolving but then something else happened... This is mostly speculation on my part but it's a widely believed scenario- The Nissan could do well at LeMans because of its impressive power output, that big feature that allowed them to compromise everything else and still have hope at the main race, but, the ACO for safety reasons introduced a 1000bhp limit to the event, for the other big teams losing ~150bhp wasn't a biggy they were racing awesome all round race cars but Nissan? They needed the big power output to pull this thing off.