If you accept that basic premise, you can then admire Navalny's courage and mission to free Russia from Putin's oppression and corruption.
Navalny was an inspiration to millions of people around the globe. He was a direct threat to Putin's power. That is why he was killed.
Most Americans do not view the world's affairs as "what benefit do I get?" But to your query, any pushback against Putin's Russia (e.g. Ukraine) is helpful to global and American security -- which is in your best interests.