I try to use "pure" gas (ethanol free) as much as possible. It produces much less carbon emissions than fuel with ethanol. GDI+ETHANOL =CARBON....2013 NAV here as well. Bought the car with 40,000 on it and was curious about all the soot on the bumper after a few months, so I started researching and learned some things about these particular GDI builds. They reposition the fuel injectors below the intake valve so the valves never get washed and build up carbon, but makes the EPA happy about efficiency and pollution. They also tend to run rich if they're idling. Blow by is intense with the GDI engines and the carbon will build up around the piston rings, apparently as early as 40,000 or less, if it was driven by a grandma (like mine before me). Just based off of what I have read about carbon build up the cat could've received a meteor of burning carbon that potentially was already plugged with hot carbon which lead to catastrophic failure of the engine unfortunately, in your case.
Intake valves are a known source of failure with GDI because of Carbon. I'm guessing the combination of the valves being on shaky ground and the meteors that inevitably caused failure to the cat had a terrible combo effect.
When my exhaust was replaced the mechanic told me the resonator was completely clogged and I knew exactly why. Heat and pressure from stomping on the accelerator will help clear this out a little I hear. I try to floor it every day as I round the corner to go home from work. I also use BG products for preventative maintenance. I know it's too late for you, but maybe others will take note.
TL;DR: I think Carbon build up caused this even though you had no warning. These engines seem to produce a lot of it.