That was a single event. Jon snow has been making stupid decisions since the first book. He gets super plot armor.
Jon Snow is not an idiot.
He's perceptive, he's a good strategist, he's a capabale leader, and he's deliberate while being open to new courses of actions.
Jon's fatal flaw is his inability to communicate with/properly express himself to his subordinates, and absorbing Aemon's advice to "kill the boy", to a more extreme extent than was necessary, which is one reason he's more closed off in Dance compared to books prior.
That's what lead to Jon's downfall, and lead to some of his more bumbling choices.
Mistakes, but not a lack of intelligence.
Hell, just look at how his advice to Stannis on rallying the Mountain Clans is playing out, amongst other things.
Trust me, I have no love for what they did to Stannis for seemingly arbitrary reasons.
Seriously, compare mopey Jon being insulted by Theon and goaded into accepting Ghost (not that he wasn't going to take Ghost anyways), with:
"An albino," Theon Greyjoy said with wry amusement. "This one will die even faster than the others."
Jon Snow gave his father's ward a long, chilling look. "I think not, Greyjoy," he said. "This one belongs to me."
Shows a world of difference in the bite that they have, amongst other qualities that differ between show/book Jon.
(And not really related to any of this, but I've always loved how heavily the Theon/Jon dynamic/parallels were set up in the first (non-prologue) chapter alone, from the moment the former kicked the deserters head and Jon called him an "ass" on, all the way down to the chapters last line which I quoted.)
