Why am I not surprised?
There's a Russian publication which has more details: http://www.vedomosti.ru/technology/articles/2016/03/17/633926-importnii-soft-zamenit
Long story short, this letter from Oracle was sparked by a request to list a Russian company called "Postgres Professional" in the federal product registry. The background is obscure, but this apparently puts them on a better footing for getting government contracts in competition with Oracle.
The people behind the company appear to have worked on the development of Postgres for some time. There appears to be no lack of technical ability. Their road map includes major improvements in high availability clustering, full text search, and indexing. They also mention migration of databases as one of their core capabilities.
In other words, Oracle isn't facing a hypothetical threat from Postgres. Rather, they're facing direct competition from a local commercial competitor who is well placed to use Postgres to take a lot of Oracle's business away from them in Russia.
The Russian government is already using Postgres, and have several more projects in the works. Postgres is used by the French government, Mastercard, and various other large Western businesses (mentioned in the above story).
Oracle's claims are completely void of any actual content, so the Postgres Professional's response was limited to saying, "Postgres is better than Oracle in all those areas".
There was an El Reg story a short while ago about Microsoft products getting the boot, and in the comments I believe I mentioned that Oracle would be next, so I'm not surprised at all by what's happening. The story above mentions that SAP is also in the government's sights due to the large sums of money being spent on SAP.
The reason behind all this is very simple. Russian government policy is to diversify their economy to become less dependent upon oil and other natural resources. This goes back to well before the recent price slump, as they were investing their high oil revenues in things like aerospace, battery tech, IT hardware, automobile production, and of course software.
Russia has a fairly large and sophisticated software development industry. Where they've mainly lacked is sales and marketing. The government is using their purchasing power to boost domestic companies to give them a head start. The intention is that they will eventually expand into foreign markets, particularly in various parts of Asia. Whether or not you happen to think they would find customers in the West is irrelevant, as they're far more interested in developing countries which are experiencing faster growth and where there are fewer incumbents who have the market already sewn up.
The plan goes well back to before the collapse in oil prices, the decline of the rouble, the Ukraine crisis, or Snowden revelations. However, all those factors have acted to give more serious attention to the diversification plan, and the low rouble has made it financially much more attractive.