RICO is always mentioned with various peccadillos with various people, but I assume (IANAL) that proving it was deliberately criminal and repetitive is the catch. Offering an expensive but crappy education is not criminal. (It just should be…)
Criminal fraud is much, much harder to prove than civil fraud. There would have to be absolutely undeniable evidence available for them to try a criminal fraud case. Most white-collar folks know not to make things so obviously in bad faith, and have a flimsy cover story good enough for reasonable doubt to creep in, but not good enough to avoid losing civil litigation.