Circumstances can change in a person’s life such that one may want to return to being a citizen of a country from which one has previously renounced citizenship. You may decide at 18 that you don’t think you want to have any ties to the place you happened to be born but from which your parents moved when you were an infant, and later in life have returned to the country in which you were born with a completely different perspective, perhaps due to business relations or a better appreciation of your predecessors’ culture. The two countries involved possibly don’t recognize dual citizenship, so you may have had to pick one at your coming of legal age and later changed your mind.
Regardless, it stands to reason that there might be people who change their minds about being a citizen of a certain country, and want to get back what they had once renounced. Is there anything stopping this in general? Is it just too hard to even get back into a country that you have renounced citizenship from? Do they treat you like a sore loser and say “you had your chance, now go away”, or do they welcome you back? I’m guessing it depends on the country, but I can’t find any information on anyone wanting to renaturalize anywhere at all.