I’m confused on the usage of this word
Try selecting the whole phrase. That usually helps to spot special expressions.
In this case you've got "you ni natta". If you select it as a whole phrase you get the meaning "came to be". "reached the point that", ...
which shows that youni + naru has a particular meaning. You can now google that particular turn of phrase to find out more, e.g. https://www.learn-japanese-adventure.com/you-ni-naru.html