Well, first I think it's necessary to correct some misconceptions. Russia wasn't necessarily feudal on the eve of WWI. Serfdom was abolished in 1862 by Alexander II. Russia did indeed have a large peasant population but it wasn't feudal. As for industrialization efforts, there was in fact a concerted effort to industrialize on the eve of WWI. Prime Minister Sergei Witte actively tried to industrialize the country and used foreign investment to do so (largely from France). The Germans were keenly aware of this and theorized that by 1917, Russia would in fact surpass German industrialization or at the very least catch up. This was in part why Germany was so eager to go to war in 1914, they knew that if they waited too long they would be unable to fight a war against both France and Russia. Moreover, Russia did have industry and some of it was quite old. Tula was a center of metallurgy in Russia going back to the Era of Peter the Great. Tula was a known manufacturer of guns and metal (famously the samovars). Granted, the industry was relatively small but it did exist.

Now to answer why Russia was behind, we have to keep in mind the Russians were actively trying to catch up. They were not unaware of the gap in industry. However, in the early 1800s when the industrial revolution was beginning Russia was in an interesting position. Post-Napoleonic Europe left two major powers on the continent: Russia and Great Britain. The rest of Europe was dramatically weakened. France had a new government and had to contend with lingering issues of nationalism and demands for rights. The German states were bled dry and in no position to challenge either Britain or Russia (though they most certainly tried). Interestingly, Britain largely left Europe to deal with their own issues. This reality left Russia as largely dominant. The tsar, at the time, Nicholas I, was keen on maintaining a conservative hold over Europe. This meant that he was for more concerned with destroying revolutions than with modernizing the country. Consequently, industrially and politically Russia stagnated a bit. Now, it must be said, much of Europe at this time was ruled by autocrats, but ideas of liberty and constitutions lingered in Europe. Nicholas actively crushed these in Russia, so they either went dormant or became radicalized but nevertheless weak. This situation began to change during the Crimean War, when Russia saw the gap between itself and Britain. Regardless, for 40 or so years the tsar did not emphasize modernization and instead clung to conservativism.

After the humiliation of Crimea, Russia did undergo a modernization program but problems soon became apparent. The new tsar, Alexander II, did want to both liberalize the country and bring it forward, but Nicholas' years of oppression caused the liberal elements to become more radicalized. Consequently, Alexander's, relatively, tame reforms were met with anger by both left and right. Elements on the left had grown so tired of conservatism, that they plotted the assassination of Alexander. They succeeded but ultimately doomed the liberal movement. The subsequent tsars, Alexander III and Nicolas II, returned to the conservative policies of Nicholas I. Thus, once again, Russia stagnated. It would take yet another humiliating loss, the Russo-Japanese War, to goad Nicholas II into seeking further modernization. Yet by then, 1905, Russia was already behind the curve.

To conclude, we have to keep in mind Russia was not some feudal state in 1914. They were behind in many areas but they were still modernizing and doing so rather fast. Nevertheless, years of conservative leaders led Russia to stagnate. Nicholas I, Alexander III, and Nicholas II were more concerned with maintaining the autocracy than modernizing. They theorized that modernization would lead to chaos and demands for reform. However, after losing to Japan, even the conservative Nicholas II realized the need to at least industrialize. Yet by that point Russia was forced to play catch-up.

In terms of sources, I would recommend Edvard Radzinsky's Alexander II: The Last Great Tsar; W. Bruce Lincoln's Nicholas I: Emperor and Autocrat of all the Russias; Catherine Evtuhov's Portrait of a Russian Province: Economy, Society, and Civilization in Nineteenth Century Nizhnii Novgorod (This book only focuses on a single province but it gives a good look and the economic realities of Russia).