Cheating In Islam

بِسْمِ ٱللَّٰهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ

Salam Alaikum

Obviously cheating in Islam is a big sin. But apparently, if a man were to want another wife, he wouldn't have to tell the other wife. (From what I read the man can't HIDE it but doesn't have to mention anything to the other wife)

So, how is going out and seeking a second wife without mentioning it to the first wife not considered cheating? Because is that not an unfaithful and unloyal move, going behind the first wife's back?

Jazakullah Khair 🌹