Anyone taking the time to organize a convention is motivated by something besides profit. This goes for anime and every other kind of convention you can name, there's just too much work involved to justify it on a personal basis. People want swag, recognition, popularity, access, or something darker, that's what keeps them going (at least until the con gets big.)
When you start to understand there are complex social motivations behind these gatherings, it's easier to understand the stories we hear are lies. Within any group of people, there are incentives to cause problems for others: maybe the accuser wants status, is bored, doesn't like the accused, or is fucking nuts. Discovering an actual predator is very rare, but gossip and power plays are the glue that binds.
I personally think it's best not to believe any stories that involve criminal activity unless a) you have seen it with your own eyes or b) there's a record of a criminal proceeding. And I'm not sure why that's not people's default, we all know lots of gossips and liars but there are comparatively few sex fiends, maniacs or kiddie diddlers in any community.
I'm sure social psychologists have a theory to explain it, but groups of people will generally believe the most outrageous story over the one that most closely resembles reality.