There are a lot of things in play. Another optional goal is to tighten up the local russian backgarden. Just like it was before Crimea snatching, population was rather frustrated with the powerholders, some bigger protests brewed in capital cities, and although they were even smaller than back then pre-Crimea, I see it as a sub-motivation, and them freely killing Navalny just after that, rolling out laws groving in their restrictiveness - I think these were their goals all along.