ことなの

ことなの is a casual form of ことなのだ, used when you want to explain, justify, or confirm a situation, often with a nuance of seeking or presenting an explanation. It can express a conclusion about a fact, or raise a clarifying point in conversation. It’s common in conversations with friends or in casual writing. The phrase tends to point to the reason or nature of something and can carry a subtle sense of assurance or expectation.