But a movie can catch on with mainstream audiences without necessarily being designed for them. The degree of Black Swan's success was a pleasant surprise, that doesn't mean anyone planned for that when it was greenlit. Awards success, maybe, but if Black Swan had made just $40m it would still be considered a hit that tripled its budget, but not in break out territory.
All directors and studios hope their movies are successful, but hope is one thing and expectation is another. A studio expecting mother! to replicate Black Swan's success or thinking a $60m spend (between the budget and P&A) would be worth it financially, well, I'll be nice and call it extremely optimstic. Critically is another story. Anyway, we've all followed movies and box office long enough to know studios can make some...interesting decisions, and certain failures are easy to spot from a mile away.
So, maybe the studio expected, say, $60m, but maybe people also aren't wrong for questioning if that was ever realistic, considering its content. Now that it's opened, though, saying "It was never meant to be commercial!" can come off like a bit of an excuse but to be fair, there was a, "Yeah, I don't know about this," argument going all along before it opened.