What explains the popularity of "strong man" leaders?

If you look back over history at periods where there is huge social upheaval, you can see it is usually correlated with technological change. Technological changes cause social changes because they alter the way that people need to interact with each other to get and distribute what we need to live and make our livelihoods. This changes the power relationships in society. It looks like this:

Technological change leads to

Changes in ways people need to produce and distribute stuff, which lead to
Changes in social power relationships, which lead to
Changes in what is acceptable to believe is "natural" or "just" in social arrangements.

It's been happening since prehistory.

Here are a couple of relatively recent examples:

1. The power of Rome and the priestly class was undercut by the invention of the printing press.
2. "Women's liberation" occurred when new household technology and the invention of the pill freed them up from domestic work and allowed them more of an involvement in the public sphere. 

Unfortunately, there is usually some kind of backlash from the rulers that are being displaced by the changes:

1. The Inquisition (the witch burning times) followed the invention of the printing press.
2. Patriarchal backlashes in the form of religious or demagogic pronouncements or regressive legislation have dogged women's efforts to have more of a public voice .

After some horrific and largely unnecessary suffering - witch burnings, stonings, wars, civil wars, for example - things generally fall into place the for better (or worse).

But note that the upheaval is not caused by individual leaders of change movements (e.g., Luther) but by social conditions that created the possibility of their messages becoming "acceptable" to believe, rather than heretical, offensive or nonsensical. I believe this happens when rigid insistence on outdated status quo explanations leads to toxic social state.

OK, so if that's clear, we begin to understand where we're at now. MASSIVE technological change: Factory automation, instant global communication, high speed transportation, increasingly viable green technologies. In other words, a global economy that threatens to thoroughly disenfranchise an even greater number of people who will be without work in what remains a wage-based economy. Erosion of social supports in favour of tax cuts - where the benefits go to the already very well off - continues to shrink the middle class while the wage gap grows and grows.

So what are today's "heretics" shouting by way of a response to these changes and what has been the backlash to them? What is becoming acceptable to believe and how is it being resisted?

The heretics are shouting "environmental sustainability", "flatter organizations", "universal income / equity", "cultural diversity" while emphasizing the importance of developing responsiveness (rather than aggressiveness) for resilience.

The backlash is shouting "jobs before the environment", "hierarchy is natural", "no freeloaders",  "your culture threatens rather than enhances my culture", while gunning for aggressive individualism.

So there we have the rise to prominence of people like Trump or other "big, loud guy" leaders who hear and capitalize (very literally) on the backlash. The voices of the backlash come from the plutocracy, from men with an unearned sense of entitlement, and from the lower-middle class who fear loss of social position if those they consider below them (women, minorities) are on the rise. 

e.g., "Spencer and other alt-right leaders see Donald Trump’s rise as the first step towards a whites-only state. "Our lived experience is being a young, white person in 21st century America, [and] seeing your identity be demeaned,” Spencer said. “I’ve lived in this multicultural mess for years and I’m trying to get out of it." - The Atlantic, "Rebranding White Nationalism"  italics added