@Fotamon It does make a difference. If he REALLY had to take one set of armor, then taking the one that stands out the most was dumb even without the GPS thing. We saw from that battle that there are loads of royal knights so you could probably pretend to be one with little issue, while dressing like one of their commanders would expose you much faster.
It's a shit comparison but it's like the difference between pretending to be the low-rank officer of some country's national army and pretending to be a general. Both options are risky but one is clearly worse than the other.
I also disagree with the "he is just too young" or "he is just dumb" excuses. The story has shown MC being clever and cunning in previous loops, even if he did fucked up from time to time, it wasn't till this loop that he went full retarded, which makes it seem more like poor writing than the author being faithful to MC's characterization (which, by the way, had him act ultra-careful to the point of paranoia before).
Hoperfully, his recent stupidity has something to do with that bone thingy the Necromancer put in his head but I doubt it.