My thoughts for what they are worth. A single serving or food item is extremely unlikely to be "the culprit". The body is an amazing thing capable of dealing with extremes in exposure to toxins, parasites, bacteria, shortages of nutrients etc etc.
There are a lot of foods that are goitrogens and a lot of those actually have some very good benefits, broccoli for example. The key is 2 fold, a diverse diet of clean (well as clean as we can get) foods AND supplementation to fill in the gaps.
Im a huge proponent of Iodine but bet a very very small percentage of people are "fixed" from Iodine alone. Also most people who suffer from thyroid issues are missing more than just Iodine but many nutrients.
Their condition is not caused by a single food item but life in general, a combination of poor food choices, exposure to toxins and simply food sources that are lacking in nutrients.
I try and tell people to not focus on the cause or specific condition but focus on giving your body what it needs. Sure your symptoms/condition can be your guide but dont put blinders on, treat your body as a whole organism and you will find the symptoms and problems will resolve in time.