I don't understand why he went back to Russia --- on principle, maybe? Regardless, it wasn't worth it. He could and should have stayed in the West and pumped out anti-regime content: he would have achieved much more. Rest in peace.
He was a Russian politician and was intending to stay one. In the eyes of Russian public opinion, a politician who fled abroad - opposition or not - is not a politician anymore, but some foreign guy living in comforts of some Germany or England, either on money stolen from Russians or on the payroll of CIA, not worth listening to. Interests of polit-emigrants and interests of Russians in Russia do not align, and the general public knows that.
This is why Navalny returned and Yashin never left.