Not just online it should be noted, this was a relationship that started offline by an introduction from long time friends - so i.e. an introduction from a trusted source which is what usually leads to someone one trusting another person, or at least being inclined to trust that person.
In second point, the article points to what leads to trust online - i.e. a letter with specific details, a willingness to be contacted in a multitude of ways (phone in this case), and a willingness to be contacted offline as well (meeting in person). Finally a willingness to offer up third-party endorcement for the claims being made.