Tim found the symbol on the cave that proved his gut feeling. Started with a feeling, found evidence. No one else even bothered.
And Red Robin did sell well, but so did Lobdell's Teen Titan's actually. It was one of the longer lasting titles in the New 52 and its own spinoffs and events.
And Batman Beyond and Young Justice which each took Tim but changed him in ways the fans didn't like, so yeah no surprise that didn't sell.
So if you want to hang your hat on the fact that the last terrible series, which launched from a poorly received thinly veiled attempt to diversify the brand from a poor selling backup with even more terrible art somehow didn't manage to set the charts on fire then you're free to do so. I just think there's a little more to it than no one wanting to read Tim stories.