The CAD industry is maturing, so one way for large companies to grow is to buy up other, smaller companies. It's a way to get more customers and to acquire technology, without taking the risk in developing (and testing and having it fail) in-house.
Sara Ferris makes in interesting point in AEC Tech News #176: My initial reaction to this news was that Autodesk felt compelled to acquire a structural analysis developer before Bentley Systems bought them all. That might be a bit of an exaggeration, but Bentley did go on a structural spending spree at the end of 2005.
Could there be a race among CAD vendors in acquiring "all the good catches" before a competitor does?