If you're going to assign blame, then I'd start with the people who sold to the rugby franchise without putting something in place to guarantee that the club would have the right to a deal at the stadium. You know, the ones who said that the critical part of the deal was that the football club would not be disadavantaged. Maybe you forgot that bit?
I don't really get why people are so worried about the legal action, if it's bullshit then it'll eventually come to an end and SISU will have to pay the loser's costs (which will be substantial). If it isn't bullshit then one potential remedy is that Wasps may have to pay more to the Council for the stadium. I don't have a particular issue with either of those outcomes.
Wasps and the Council must have been well aware that the deal that they were doing had elements of legal risk, especially given the past history of the stadium and the SISU/Council court battles. Presumably this is why there were the flat-out lies from the council denying it, and all of the other secrecy around the sale. Wasps and the Council chose to push on and take that risk - why would I have sympathy about them having to defend it until the legal process is exhausted? It's the way the law works.
There's no actual reason for this to stop Wasps doing a short-term deal with the club, as they have done before. People who want to pitch it as all SISU's fault are looking at it with one-eye closed, imho.