The current rumor being spread on Russian channels is that Durov went to France knowing that he would be arrested in order to avoid extradition to the US. Apparently Durov believed that the US government would be coming after him, for much the same reason as the French government. He apparently believes that in France he will have a better chance of cutting a favorable deal to protect himself from serious jail time, while avoiding the possibility of extradition to the US because France does not respond to extradition requests of French citizens.