Aliens had to evolve and would have the traits that most animals, inclusive of humans, have. So its a safe bet that the curiousity to explore is deeply rooted in the aliens adaptive psychology to do so with the obvious benifit to exploit what new discoverings it finds. Its not just humans that subjugate those with less advantage, its a trait in almost any animal, whether its concious or a product of opportunity the effects are the same...
This is your assumption, but really you have no way of knowing. All of our experience in dealing with life forms comes from terrestrial origins. Even if we both started out as similar single cells, their psychology, if that even applies, as well as their physiology may have diverged so early in the evolutionary timeline from terrestrial life that we have absolutely no way of knowing what thought processes they may or may not possess.
To use a fictional example.
In
Ender's Game, we find that the near complete xenocide of the Formics was the result of not only the two species, Human and Formic, difference in physiology, but mostly due to completely different ways of thought process and motivation for expansion.