Martyrdom. Navalny knew what it would mean to return; he also knew the risk of not returning (constantly trying to avoid shitty assassination attempts with collateral damage).
Speaking of... When was the last time we heard from Snowden? Haven't seen his name in the media since basically the start of the Russian invasion of Ukraine.
That's the story he tells, at least. He just so happened to fly to Moscow alongside a Kremlin intelligence asset the day after his US passport was revoked and then, oopsie, he had to stay there; never you mind that there were direct flights from Hong Kong to Ecuador, he had to go through Moscow to get there because... reasons.
I don't know whether it had a significant impact in Russia, but the rest of the world only knows/cares about the guy because he went back. Otherwise he'd just be yet another person murdered by Putin's regime.