Fister squeezed as much money out of the business as he could between June 2004 and June 2008, yielding to the desires of the short term market analysts and his own compensation plan, I would imagine. In the process Fister and Porter slashed R&D (operating margins), while Bushby and his ilk found new accounting gimmicks like EDA cards to accelerate income.
The scheme probably could have continued with a pipeline of new products from outside of Cadence had Cadence not hit the wall (and credit crisis headwinds) just as they were attempting to pick off Mentor.
It will be interesting to see if Fister's attempts to separate Cadence from the rest of the industry by dropping out of EDAC, DAC, etc. will leave them hanging in the wind or if Cadence will find a new sense of collaboration.