How can I pass my PhD thesis defense when nothing has been successful?
The specifics here are certainly best discussed with your advisor. They should know about your discipline, and how to frame results in a way that is suitable for the community.


  Has anybody done a "fully failed" PhD defense ... and passed? How would one do this?


For me, it does not sound at all like you "failed" in your PhD. A PhD is a research project, not a product. Ultimately, you (and your committee) should not evaluate your results based on whether they ended up being useful, but based on whether you had a reasonable thesis and a thorough scientific study of this thesis.

That is, if you proposed a novel approach, collected reasonable data, and thoroughly validated your initial thesis, your research was successful, independently of whether this approach then ended up being used in the larger project context. Sure, it would be nice to be able to say that your approach has then helped these other people to do A, B, C, and D, but the real world does not always work like that.

To me, it is mainly a question of mindset. If you yourself consider your PhD "failed" you will have a hard time selling it to a committee. You need to embrace the idea that you did good research, and not measure the success of your own work on factors outside of your control. In that sense, you should defend what you did and why. You can, and maybe should, discuss why it ended up not being used if there are interesting lessons learned, but stay away from political or interpersonal arguments (these can indeed sound whiney). Stay positive and focus on what you did, not on how much other people then liked the results.