I'm sure he has powerful friends, but dude is really going for it because he's at their mercy while in prison or in Russia in general. Putin has a decision to make. If he waits too long, killing this dude is going to end up being his demise, but he's also right now morphing into Putin's biggest threat, ever.
Putin can personally walk Navalny on the roof on the magnificent
Kazan Cathedral (below) on Nevsky and push him off the edge to
his death on the concrete floor below, and absolutely nothing can
happen to him.
Russia is an extremely powerful country that does not need anyone.
It has more of everything than any other country has, and unlike the
Democratic Republic of Congo, and Saudi Arabias of this world, it
has the minds, the money and the manpower to exploit its own
natural resources. Furthermore, it has more money in the bank than
the US, Germany and the UK have.
This is the point Putin was trying to convey when he nabbed Navalny
at the airport the moment he arrived in Moscow.
If Putin shot Navalny in broad day light, there is not a damn thing any
one could do.
Russia can destroy the world.