I didn't question the decision at the time, nor do I question it now. It serves no purpose. It's done and we can't go back. The front office thought they were one QB away from a SB and Cousins was the top guy available. Dumping all that money into the QB position cripples your ability to address other issues, though. However, the type of money the Vikings spent is the kind of money you spend on a player who can win you games in spite of other weaknesses. Doesn't appear that Cousins is that (hindsight being 20/20).
I agree on almost all of that, hopefully salary cap increases along with dropping other fat contracts at less critical positions will allow them to address some of the other issues.
Also - though I fully expected them to go OL when they took Hughes last year, the OL wasn't too different from the previous year (during the offseason). You don't expect Easton to be lost for the season, or to have to go to O'Neill so early because of injury, or Elflein to regress slightly (maybe due to slow start from injury recovery at beginning of season). They remained pretty healthy in 2017 if I remember correctly, which maybe gave them a false sense of safety at the position that really actually needed to be improved for depth.