How Accurate Is It To Say That The Growth of Reformist Groups In The Years From 1881 Was The Main Cause Of The 1905 Revolution?

I do not think that it is very accurate to say that the activity of reformist groups was the main reason for the 1905 revolution since there were only two parties really mentioned, and they were mostly threats with no action. More prominent causes were social economic and political preconditions, the Russo-Japanese war and Bloody Sunday.
The most important cause of the 1905 revolution were the preconditions, especially social and economic ones. The vast majority of the Russian population were peasants living in extreme poverty, especially industry and agriculture workers, even though the economy was thriving, apart from the agricultural side of it. The Russian population was growing rapidly and there was no space for them all too live and cities like Moscow and St Petersburg were full of slums. There was not enough food to harvest, leading to famines in 1892, 1898 and 1901. Conditions like this led to the trigger conditions that set off revolutionary activities like Bloody Sunday, and other strikes and protests.
The second most important cause of the 1905 revolution was Bloody Sunday which happened on the 9th January 1905, according to the Russian calendar. It had started off as a peaceful demonstration led by a priest named Father Gapon. Suddenly the Russian army units opened fire on an unarmed group of protesters marching on St Petersburg’s Winter Palace to present the Tsar with a petition calling for constitution. It was a disaster for the Tsar and the middle classes and workers were appalled by the peaceful demonstrators being shot down. Bloody Sunday led to many of the exiled reformists from Social Democrats returning to Russia to try to force political change with the help of the widespread unrest. It also led to mutinies in the