What bigger picture? The bigger picture is that under Mourinho we didn't get close to challenging for a major title, and that his best season was mostly due to de Gea. You can't argue against this fact with the evidence stacked against you.
United had the 2nd best defense in the league in terms of goals scored against, which was the main reason we finished in 2nd. Only 1 more than City, but 8 less than Spurs. Despite this, Mourinho thought United needed a boost in defense. Why? Because he knew that mostly came from de Gea's brilliance.
United had conceded the most shots on goal of all the top 6 sides. Yet United had the 2nd best defensive record. We also had the 5th best expected goals against, outdoing it by 15 goals. Why is it that our goals conceded stat directly opposed Mourinho's defensive transfer plans and the shots on goal conceded stat? The answer is obvious. de Gea carried our defense. de Gea was voted as the Matt Busby player of the year, and voted by the players as the best player of the year. Strong correlation there isn't it?
Meanwhile, we had created the least amount of chances out of all the top 6 sides. Our expected goals was 6th best in the league.
All of this points to de Gea saving us. That's the context of that 2nd season which Mourinho fans love to brag about. Once again, this is backed up by our eyes where we were clearly awful on the eye. And what do you know, that position is the one position that could escape Mourinho's crap football.