What seems to have happened with humans is that the limit rose a bit higher than usual, probably through reproductive competition - but not high enough to be truly smart.
Darwinian solutions are always short-term and instinctive, and more effective in the short term - which is fine as far as it goes, but creates a reproductive cost for the more strategic kinds of intelligence which are capable of planning ahead.
Long term solutions are likely to frustrate any number of hard-wired tendencies, and that's not going to make them popular, or likely, with individuals who don't have the cognitive or empathic skills needed to understand why they're necessary.
And so - most species won't make it. You may get a sudden die-off, or you may get cycles. But breaking out of that pattern is going to take a lot of luck, and some stray well-intentioned randomness.
