I disagree. There are plenty of books/series that have huge visibility,and plenty of readers who thought they were 'good enough', but they don't become the huge phenomenon that Twilight became. I can't count the times I've seen 'the next Twilight' or 'the next Harry Potter', but Twilight has been around for 15 years, and Harry Potter for 23 years, and there's never been anything that approaches either of them in popularity. So no, I don't think you could have put just any author in Meyer's place (or JK Rowling's) and got the same result. There was something about those books that made them take off the way they did, and it wasn't just marketing.
In order to be a bestseller, no, it's not a particularly high bar. These days, all we need is to be in a box set with 20 other people for $0.99 and chuck a lot of money at ads. You're on the list for one week and you get your letters, bang. But to be a true runaway bestseller like Twilight or Harry Potter, on the bestseller lists for weeks on end, that takes a lot more than just buying visibility.
Meyers and Rowling were picked by random chance off the slush pile, and pushed to a degree you don't see anymore, and established in a completely different economic and social climate which was far less risk averse. Couple that with the passage of time, and of course they've attained a level of popularity no one else can approach. But, that misses the point, and comparing them to indies vying for the bestsellers charts today is like comparing apples to chainsaws.
Why was 'x' laundry detergent formula built into the Tide brand versus another formula which could have been proven to be far more effective? Why do we all know of Tide, but have never heard of the other? Because one of them got the push, and the other one didn't. Multiply that with the passage of time and you have a brand firmly entrenched.
Meyer and Rowling were both pushed to an insane degree. The visibility for their books was off the charts. Book chains were still big. Indie competition was not yet a thing, i.e. trads reigned supreme. They got their movie adaptations made pretty quickly. Hype and publicity was paid for in full. It was a machine running at high rev.
Point being, Twilight and Harry Potter and any other bestseller you can name are not bestsellers based on merit, special-ness, or talent from a writing or storytelling perspective.
It's not like the Twilight and Harry Potter stories themselves are any great shakes. They're serviceable in that they're accessible and easy reads, and vampires and magic have always been popular. But, they're not particularly original from a storytelling standpoint, and nor do they have to be since readers in general have never been that picky. Sure, you could say nothing has come close in popularity, but I would argue nothing has come close in terms of visibility either, and all of the factors at play at that time which also contributed to said visibility. The popularity and the visibility, however it was attained - they go hand-in-hand. Visibility begets visibility.
We use hindsight to attribute things to those kind of success stories, but I think it sometimes leads to false conclusions.
Guaranteed at the time Meyer and Rowling broke big there were similar books by other authors that featured better storylines, more interesting characters, the whole nine, and the reason we don't know their names is because they weren't picked, and they weren't pushed. Why? A million reasons. The most likely being that they never became visible to the right people at the right time. Fickle-ness outdoes merit all the time. In other words, random chance.
Writers and authors have this tendency to see writing, authorship, publishing, and bestseller-dom as a meritocracy.
There is no meritocracy. There is only what's seen and what is unseen.