Here are three other matters to factor in, firstly the validity of the pre WW1 publicity on peace. We have to look at the nature of public statements at the time. Since when were such pronouncements not political spin?
Second; it would be possible to quote from a range of opinions and select the ones which support your argument. Propaganda merchants such as the WTBTS never do anything else; they have absolutely no sense of honest objectivity.
Yes there was a spirit of optimism before the First World War because of scientific discoveries such as pasteurisation, anaesthetics etc serious diseases such as syphilis had just been understood and modernism in art, think of Picasso, Marcel Duchamp. These were among reasons to see progress and a brighter future.The assassain's bullet in Sarajevo was the catalyst to mobilise existing tensions to war but afterwards the world and it's hope in humanity and with tangible progress in civilisation, continued with setbacks as it does today.
Thirdly the Watchtower in its tradition of narcissist leadership, expressed the personal and normative interpretations of its chief theologian Frederick Franz. After Russell’s prophetic disaster and seeing his own life figuring in the imaginary unfolding of God’s plan, the self-obsessed Franz projected his own experience centring on the year of his own baptism 1914. It was a turning point for him...and therefore the world.
This could well account for the WT mantra of “the generation of 1914.”
Let’s not forget regarding the year 1914 Russell got it entirely wrong, he had foretold world peace and the death of all the 'ungodly' by then.