He could have gained respect/acceptance if he took a different castle, white harbor for example, which would be better because historically they hold coastal areas. He chose to take winterfell to try and prove to his father he wasn't a stark, even though taking castles of stark bannermen would have done the same. Like yara said, winterfell is too far from the sea and he'd never hold it. That was straight arrogant, ignorant stupidity on his last thinking he could hold it at all. All he did was poke an africanized killer bee nest lol
Honestly I think his father was going to congratulate him on taking winterfell (if theon left with yara when she said father wants a word), he probably would have given him more ships and men and a stern lesson on how they have only conquered coastal areas in the past.
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