Most evolutionary pressures are easily solved via physical rather than mental improvements. Even situations in which a smarter animal would do better are usually solvable through other, simpler solutions, making the possibility that those solutions will arise higher; fewer mutations need to happen.
Thus while incredibly intelligent combat tactics are very useful, it's far more common to see incredibly strong animals than incredibly smart ones. A human can outsmart a gorilla, but without strong tools that take a lot of time to learn how to make, not to mention build, the gorilla can tear the human to shreds no matter how much smarter the person is. The gorilla is faster, stronger, and more terrifying.
Additionally, it is also a choice between the two; brains like ours take enormous amounts of energy to run, and we only have so much oxygen with which to run our bodies.
That said, there are some situations in which there is no substitute for intelligence. Complex social interaction is one of them. Our gorilla - let's call them Yog - might be able to kill everyone, but if their weaker sibling Mog is socially smarter than them, Mog is going to be the one who gets better status. That status can translate to better protection from other gorillas, better food, and more mates. Thus Mog is more genetically successful than Yog.
Of course, if Mog is too weak then Yog might gain dominance anyways. But those sorts of evolutionary pressures make it possible to end up with a species of Mogs.
Another evolutionary pressure that can lead to intelligence is the need to coordinate. Most insects, even social ones, do work on a solitary basis without needing to coordinate with other insects to complete tasks or accomplish goals. Even when they are working together on a single task, they are usually on an individual basis doing the exact same thing; it's just that a lot of them are doing it at once. Humans coordinate. In order to complete even tasks that we view as incredibly simple for the group, it is necessary or efficient for each individual involved to be doing something completely different from the others while being generally aware of the task as a whole. Consider cooking in a restaurant; the head chef directs each individual and may be cooking the end product, the prep cook cuts the pieces, a sous chef may be creating the necessary sauces, and yet another worker may be providing the correct dishes. They are all additionally aware of the entire recipe while they complete their task, and are generally aware of how the process is advancing.
So if you want your Vosians to be sapient, a good way to make it plausible is to ensure that:
There is plenty of oxygen or other energy-releasing gases or chemicals on their planet (this has the bonus of making their relatively large size more plausible),
Each individual must deal with complex social situations, and
The Vosians must coordinate complex tasks in which each individual has a different function in order to survive.
I would also like to add that in all earthbound social insects, the queen is not the leader; she is merely the reproductive organ of the colony, treated well for her necessity, but completely cut off from the functions that run the rest of the colony. Your Vosian queens are unusual in that sense. So it may be worth thinking about what makes them different.
Perhaps they are the only source of an important chemical that enables Vosians to recognize that they are from the same hive, and they withhold that chemical from those that do not do what they say. Perhaps they hold themselves hostage, threatening to hurt themselves and thus grind the colony to a reproductive and productive halt if the colony does not act in their interests. Perhaps they are simply the smartest Vosians and so queen-led societies tend to perform better. Or something else. Regardless, best of luck with your insectoid creatures. :)