The people of Kherson don’t want to be part of Russia. Why is Russia trying to annex it?

Russia is building a buffer zone to push the site of potential NATO bases and weapons systems further and further from Moscow, and to be able to militarily hold that buffer zone (requiring infrastructure, transportation, continuity with Crimea which was annexed for similar reasons, etc.). It views NATO expansion and encirclement as an existential threat, for pretty good historic reasons.

You’re right that its intentions aren’t altruistic as other users are claiming/implying. It is a nation-state. But its intentions are predictable and inline with those that basically every other nation-state would have in the same situation, because that is the nature of the institution.