Wasn't the iPhone 4 wildly successful though? It's when I got my first smartphone, so maybe my memory is biased.

Insofar as the fix to the Antennagate issue was to use a case (to avoid bridging the two antennas connected to the rim of the phone with your sadly-conductive skin), it didn't really affect the vast majority of people who bought the phone and immediately put it into a case to protect their expensive device.

The iPhone 4 was successful and even despite the fake controversy, the GSM version sold for three years without any changes.

What fake controversy? There was a real design flaw that apple responded to by insulting the intelligence of their users.

The same design flaw that contemporary phones had?

Contemporary phones did not have that design flaw. The antenna on the iPhones was exposed externally and could be shorted out, making it non-functional. Name a contemporary smart phone that also allowed you to short it's antenna by holding it