If anything, I would suspect it was primarily CCGs. Shortly after MtG came out, at cons I couldn't find anyone who wanted to play D&D (they were all doing MtG tournaments, or to a lesser degree LARPing). In previous years, I couldn't find game space because all the tables were RPGA games or folks would just come up to me out of the blue and ask to play a D&D game (even with no tables free, it was just a "play in the hall" thing). That didn't pick back up until 3E dropped, but even then it was only a brief surge and nowhere near like the years prior to MtG.