Not necessarily. I don't remember whether it was in UT, Silm or HoME, but there was a mention that he was a maiar of Yavanna - a Vala responsible for all growing things. Therefore, it is entirely possible that, in becoming "envenomed of the many beast and birds", he actually was fulfilling his purpose - whether by intent or not.I think that was his own doing more than his purpose.
“indeed, of all the istari, one only remained faithful.... for Radgast, the fourth, become envenomed of the many beast and birds that dwelt in Middle-earth, and forsook elves, men and spent his days among the wild creatures.”
-Unfinished tales The Istari