If one took the long-term "buy and hold" strategy, there would be no reason not to include Russia in your portfolio, in proportion to its relative market cap.

Of course, "buy and hold" would have been very wrong in that era (two of your superpowers would permanently tank), as it might be in this one.

Or the UK, France, and Germany during WW1. Seems suboptimal.

Not in 1916 but why not in 1890 ?

Because the country just got over serfdom, corruption was rampant, and its imperial ambitions were too big for its boots?