Yeah the Ducks were definitely building towards making a deal like this at some point. Just weren't going to have room for Mintyukov, Drysdale, Luneau, Zellweger (likely ready by next year) all to play an offensive, puck moving game. Always seemed likely that one of Drysdale or Zellweger would get moved for a big forward piece.
The timing just sort of caught me off guard, seemed out of left field at first but makes sense upon further reflection. The Flyers have quietly been contemplating moving Gauthier ever since he wouldn't report to their summer prospects camp. The nail in the coffin came when he refused to meet with their top brass during the WJC, then went on to have a big tournament bringing his value to a peak. Drysdale has also looked really good since returning from his latest injury, so at this point I can understand why both teams felt more comfortable/excited with what they were receiving.
There were some question marks about whether Gauthier belongs at center but that's no longer an issue, as his natural fit for Anaheim would be as a big scoring winger for Carlsson, McTavish or Zegras (if the latter stays at center himself)