why he doing that? In my opinion, it could be due to low self-esteem or past experiences. Putting others down might be their way of coping, trying to feel important, seen, or even appreciated. A healthy individual with strong self-esteem wouldn’t feel the need to belittle others; instead, they’d uplift and support them. However, someone who’s broken may constantly feel undervalued and seek validation by putting others down (“See, I’m better than you”).
My suggestion is to try to be compassionate and understanding towards them, if possible. But if their behavior becomes unbearable for you, leaving might be the only option. Just keep in mind that there’s likely something deeper influencing their actions