If it was an agreement to flip on trump you might have something. However, it is not. It an agreement to truthfully testify, which could have been given out of a number of reasons, such as desperation.
Tom, are you familiar with subtext? Of course the plea agreement doesn't explicitly say that she must flip on Trump. However, one can reasonably infer from the way that plea agreements work in general that she would not have been offered such a sweet plea agreement if she wasn't expected to flip.
According to the left the walls have been closing in on Trump for 9 years now, for a wide range of crimes which are totally provable in court but somehow falls apart. Surely, you have him now. 
What exactly has fallen apart? He already lost one E. Jean Carrol case and is looking at another one in a few months. He has already been found guilty of fraud in a civil trial in New York, so that's not a good sign. Plus there are 91 well detailed felony charges that have been filed. Oh, and a number of co-defendants are taking sweet plea deals that require them to provide "truthful testimony" in future trials against Trump. So yes, I think that it's pretty safe to say that the walls are closing in.