Which makes me think that seaweed was staple food at some time right? We wouldn't have evolved to need more iodine than we can get in our environment otherwise...
Evolution works through reproduction so any condition that doesn't impact survival until sexual maturity is unlikely to face any evolutionary pressure. Since humans are tribal and took care of their offspring in group settings, survivability after procreation also has little effect.
[1] https://iris.who.int/bitstream/handle/10665/43010/9241592001...
Diseases that impact even just appearance can surely make you less attractive as a mate though. And larger goiters can impede breathing or swallowing. So I'd be suspicious of the idea that we've been significantly deficient in iodine for extended periods of our evolutionary history.
I’d be far more suspicious of applying modern standards of beauty to humans that lived hundreds of thousands of years ago.
Ruminants are more efficient at absorbing nutrients from plant material due their digestive system, and this is how they get iodine in non-coastal areas.
All vertebrates have thyroid glands and there is a very similar organ in marine chordates: https://en.wikipedia.org/wiki/Endostyle. So this is an organ that likely emerged when our biological ancestors still lived in a iodine-rich environment.