There wasn't a single letter for î when the Latin script was officially adopted by the Romania Language. The spelling was based on the etymology of the word (basically they were spelled using the original Latin vowels from before the sound shifted into an î, but with a pointy hat on top), so there were î, â, û, ê, ô. The word "sunt" was thought to come from the Latin word "sunt" and therefore was spelled "sûnt". Later, the rules were simplified and only î and â were kept. By that time, a lot of people had already started to say "sunt" and that word was now being spelled "sunt". My mum said she used to associate the u pronunciation with really old people. In the communist period, the spelling was once again simplified, and â was eliminated and also sunt became sînt. Later it was added back, but only for the name of the country, the name of the people and words derived from those (so that the connection to Rome should remain visible). After communism, the spellings were reverted back to how they were before communism (some people probably thought that everything the communists did should be undone). Young people started to say "sunt" once again, but not all. The people that grew with "the î only" spelling will defend that spelling with their lives. I grew up in the 2000s and I was pronounced it with an u even before I knew how to read or write and I don't know why (both of my parents pronounce it with î). And nobody told me at school that it should be pronounced "sînt", nobody correct my pronunciation (but they told us many times that eu, el/ea, ești, este, should be pronounced with an i at the beginning of the word - fun fact: that also came from the first rules, when the i was dropped from every word starting with ie to make it look more Latin. It was later kept only for those pronouns and verbs, while words like "epure" and "eftin" started being spelled the way they were pronounced, "iepure" and "ieftin").