OK, see what you're saying. Let's just run this scenario one more time.
Wasps go bust - ACL goes into Admin. The lease probably reverts to the council at this point, although it may suit them to allow it to remain with ACL perhaps, depending on whether there's a deal to be done with someone else perhaps.
Effectively though the council becomes a creditor - what makes you think anyone would buy ACL including the full liability at this point? It seems unlikely there will be a long line of sports clubs bidding.
Wasps can't buy it, we're saying they've folded. CCFC may have moved out or gone bust, or may be reluctant to take on the full liability, or most likely would delight in seeing the council burn regardless (if SISU are still in charge). Who else would take on ACL with the full liability? The point of admin, as we've seen, is to enable the reduction of debts and liabilities.
There's a genuine risk here, to my mind. The lower risk play for CCFC, as I've said, was SISU's where the debt to the council was at least discharged at the point that ACL was sold. That obviously failed, not least because of SISU, but it doesn't mean that the deal the council have done now is any better.