I just saw a headline asking "Has There Been Any Conversation Among The Cabinet Members About Invoking The 25th Amendment?"

I'm sure there has, but every discussion has probably ended with something like, "but what do we do about Kamala?" or "but Kamala could be worse!" At this point the primary thing keeping Biden in office is the fact that nobody (Democrat, Republican, or Independent) wants a President Harris.

Maybe that is why the Bidens picked her.