How much money has Clinton raised and spent on her campaign? A lot of people have spent a lot of money on the theory that she is and will be a serious candidate and will get the nomination. Follow the money - no way her candidacy is a ruse to fool Republicans.
On the other hand, if she looses to Sanders in CA, and starts loosing to Trump in the head to head polls ( she’s behind in the most recent Rassumssen), then Biden might jump in to save the day.
But this has not been preplanned to happen.
No, but it could be a ruse to fool Democrats.