Why do people disappear?

It seems like when I'm manic, people think I'm hilarious and it's like I have a ton of friends.

But then I crash and everyone disappears. I know part of it is I stop reaching out, but people in general stop responding to me. And this isolation exacerbates the psychosis and suicidal ideation I already experience with depression.

Why do people disappear NOW, when I need them most?