Hi @LizzieLou and welcome to the forums.
That is one of the reasons I didn't leave my estranged husband .... it seemed incongruous to leave someone because they were unwell ..... but unfortunately without insight and treatment, a mentally unwell person can over-extend or emotionally impact so badly on others arroyos then as to cause everyone else in the environment to be under mental health support and treatment.
I still feel it was the safest course of action for us, and he has now left under highly disrespectful and contentious circumstances .... but there too goes his privacy. It will b come obvious progressively just how unwell he is, and by consequence, just how much we have handled "in-house" up to this point.
I think the hardest part coming through all that was that he is actually allowed to be that unwell ... if he knows enough to conceal the symptoms, then he knows enough to know that he is unwell.