In terms of your assertion that it is clearly false because kids were going OTD before the Internet, it may be a question of numbers. There have probably been kids going off since the world was created, but the question is how many. There seems to have been an explosion in recent years,
It depends on how you define OTD. Is smoking OTD? Kayin killed Heval in a fight is that OTD? As far as there being an explosion in recent years. about 50 years ago about 25% of yeshiva graduates went to college and went off the derech so actually fewer people are going OTD. The internet just makes it easier an more accessible to get things that will encourage people to go OTD. While before you would need to go out and search for it, the internet brings it straight to your home.