So Russia continues modernizing, industrializing, becoming more involved in European affairs and European, and peaks in the mid-to-late 1800s, thousands of factories opening up, Rachmaninoff, Dostoyevsky, etc.
Here's the first phase of tragedy though. Revolutionaries in France and elsewhere set up a "reactionary" government in Russia and elsewhere. This means the trend towards greater freedom, prosperity, and development is reversed. Russification becomes emphasized in universities as czars try to return to the good old days of being isolated, backwards, and xenophobic.
The people are increasingly pissed by this oppression, becoming enemies to their rulers, assassinating one, and their rulers yield by freeing the serfs. But the serf-freeing deal varies by area and for many indebts them more heavily than they were as serfs (who were gaining rights to travel and pay their dues in cities) so civil unrest is reaching a peak, things'll get tragic...>>25641714
It's a self-correcting problem.
Poland's aristocracy was too developed, impressive to Lithuanians but impoverishing their people and slowing their rate of development. This, combined with foolish designs like the invitation policy and forming laws with temporary councils which produce nothing if every decision isn't unanimous resulted in them losing authority to the point Russia, Prussia and Austria partitioned their land away.
If Poland was freer it'd be more prosperous and spread its' influence.