RUSSIA in first half of 19th Century. 1801-55
The groundwork for a modern European Russia, laid down in the previous century by Peter the Great and Catherine the Great, was eschewed by Alexander I (1801-25) and his younger brother, Nicholas I (1825-55).
Why? The answer to the question is the seismic events which took place in France in the summer of 1789 - The French Revolution. Everybody and everywhere in Europe would be affected by the wars of Napoleon and by the ideas of The Revolution.
Alexander I was able to push Napoleon's Army out of Russia following the French invasion of 1812, but dealing with ideas was much more difficult. Both he and Nicholas I fell back on the the well trodden path of Russian repression of threatening ideas.
Russia turned towards its Slavic heritage and away from its European. As a result isolationism spawned hubris, and the Russian Army was exposed, despite the vast resources poured into it (misspent on colourful uniforms), during The Crimean War at the end of Nicholas' reign. They said Nicholas died a broken man.
And well he might have done, because Russia was again in a dark place. A crisis that the new Tsar Alexander II would have to meet in the second half of the century.