This is a very interesting set of observations and very plausible. The problem is that the potentially plausible scenarios are infinite. Each of see those which we are sympathetic too as likely and others as unlikely. However, historians will connect them after the fact, not before they happen. The major flaw or bias in your scenario is exemplified by this statement, “Ignoring and mocking the experts , as people are doing around Brexit and Trump’s campaign”.
Who are the experts in predicting the future? There are none and that’s the real point. Every opinion is valid. In 100 years, historians may well point to the string of events which show that Brexit and Trump prevented another major World War — not cause it.
I will suggest another bias in your analysis. Trump has not stated that he would not honor America’s commitment to NATO. That’s a fallacy presented by the media. You need to research deeper. He has said that each of the nations in NATO need to pay their fair share. So long as they do that (which would likely be negotiated in advance of an incident requiring action), then America will stand by NATO. America spends more on NATO than any other country and more than twice as much as any countries other than Germany, France and Britain. I think it’s fair to ask the European nations to spend more — because America has its own issues to address and we need the money.
I will present a VERY simplistic, alternative version. Suppose that Trump being elected, causes the financial support of NATO to be renegotiated and along with Brexit — ultimately causes the majority of the European nations and their citizens to take a renewed interest in self protection and independence; which then acts as a wall to the continued entry of Terrorists into Western Democracies — thus re-stabilizing the region. A more stable Europe, with stronger borders then creates renewed focus and opportunity for democracies to flourish in the Middle East — thus creating a new era of peace that lasts another abnormally long time, when viewed against human history.
That scenario is as plausible as is yours.