The big question is what Russia has to gain from this. Is it just to troll the US?
Never thought I'd need to lecture HN about Occam's Razor: Permanent residency is a status for foreign citizens, who have been residing in the country permanently i.e. living there for a long time (e.g. 7 years) and might stay indefinitely. Rather than applying for a visa renewal every year, it saves time and money to grant those people a permanent residency.
The standard requirement for a permanent residency in Russia is 1 year in on a temporary residency. Honestly, I'm surprised he hasn't been given a permanent one before.