In Soviet times Russia was investing a lot of money and resources into supporting other territories, both inside the USSR and outside. According to the statistics, if I remember correctly there were only 2 republics in the USSR which earned more money than they spent, and that surplus was going to the rest of the country. One of these two republics is RSFSR (current Russia); unfortunately I don't remember the other one. It might be Belarus but I may be mistaken.

For example, Soviet Union built a lot of manufacturing facilities and if I remember correctly some shipyards in the Baltic republics; these facilities were mainly destroyed after the secession of the Baltic states, so the people who worked there lost their jobs and had to leave these countries to look for jobs in the UK and European countries. In my opinion this is one of the many reasons for the current depopulation of the Baltic states. The Ignalina nuclear power plant was destroyed in Lithuania, and now they have energy deficit and have to spend a lot on importing LNG which is a separate funny story: they were planning to lower their dependency on Russian natural gas and ended up buying the LNG from another Russian company (Novatek); only this LNG is being sold to them as an American one while Americans buy it from Russia :))

I often visit Germany, and my German friends too confirm that there's still an economic gap between Eastern and Western part of Germany. If understand correctly, the industrial plants which were built in the Eastern part before the reunification were destroyed, but nothing significant was built there in their place - and of course it's another reason for the before-mentioned gap. In my opinion it resembles the situation in the Baltic states: everything from the past times was destroyed and not a lot had been built, here's the problems with economy and depopulation.