I don't think this is plausible. How did they become smarter than humans?
The most plausible route to Intelligence is that it evolves in an environment where it is useful, that is where it exists in all known intelligent species in real life. That pretty much excludes apex predators, they only need a limited amount of intelligence and rely primarily on brawn: Look at the Great White, look at the Lion. They don't rely on strategy, they rely on claws, teeth, speed and brute strength. None of which we humans are blessed with; we did not "grow up" as apex predators, we grew up as their prey; one can see that in the archaeological record. And, unarmed and naked on a field, the best of us have little chance against a young male tiger, even one our own weight.
What is the evolutionary pressure that caused these creatures to become increasingly intelligent over millions of years?
For the purpose of this discussion, consider "intelligent" as being better able to mentally model nature, prey and predators: Increasing intelligence is better models; along with the mental ability to use these models to simulate various outcomes: Letting them set traps for prey, or make themselves safe from predators by devising barricades they cannot figure out how to circumvent, to kill remotely (like we did with spears and slings), etc. In other words, these simulations allow imagination.
Eventually, in humans, we had runaway intelligence; one hypothesis is that at some point we were safe enough from nature that our biggest threats came from other humans, and that self-referential evolutionary pressure to outwit our own species became a maximizing feedback loop; meaning we became as smart as our biology could evolve to be, without further mutations killing us.
For your creatures, their biology could perhaps be pushed further, but you need an outside driver to push them to the tipping point, where they are their own biggest threat. An easy route toward that is basically the human route: we are one of the weakest and most pathetic animals on the planet! In terms of eyesight, hearing, olfactory sense, tasting sense. We have poor speed, poor strength (even compared to a chimp), poor reflexes, pathetic 'claws', poor canines, poor hide for any kind of protection. We are born defenseless and stay that way for years (compared to hours for other animals).
Apex predators don't have those problems, so their survival does not depend on their intelligence. Since brains are massive fuel hogs and evolution is ruthless in conserving energy to prolong survival, only animals whose very survival (at current levels) depends upon intelligence will continue to have it. It is always very easy to evolve toward less intelligence, and very hard to evolve toward more intelligence. Predators do need predictive models of their prey and their own capabilities, perhaps how to track and find them. That is more than their prey needs but not a particularly high level of intelligence.
With regard to biologically expensive intelligence, the path of least resistance for all animals is "just enough to survive and reproduce." The Jar'keth need a reason to be mortally terrified of something, so every little bit more intelligence (accuracy of prediction) they evolve means more of them avoid early death.