I'm betting that Nickelodeon Universe at MOA was the straw that broke the camels back. I'm sure that CF wanted exclusive Theme Park rights to the characters, but then Nick strikes a deal with MOA and essentially sours the deal. I personally blame Nickelodeon, they really should have thought about the CF deals before they decided to do NickU. So by 2010 Nick will be out of all Universal and former Paramount Parks and have a grand total of one theme park.
I suppose it's kind of stupid for CF too, though, Nick is way more relevant and will sell more tickets than Snoopy ever will.