All the examples of people who profit off fear: mass media, lawyers, politicians, and industrial pharmaceuticals have all existed for decades longer than the current age of fear. That makes them insufficient as a cause. There must be something else.
And that is western world. Look elsewhere, you can find tons of inescapable unfair misery (150 million dalits in india, anyone?).
Add peer pressure, instant seeing of highlights of other's lives which makes some depressed.
Also is the shift from mass broadcasting to targeted messaging. The degree of information available to exploit you, your weaknesses and biases is a new phenomenon.
The erosion of social loyalties and ties, which can be linked to one century of neoliberal policies, is also a change (although it happened in the past: see the Corruption and decline of Rome: http://www.historytoday.com/stephen-williams/corruption-and-...)
I think fear is a natural human attribute left over from an earlier time in human existence, I really do.
From a young age, if we're lucky enough to have parents, we flock to them because we perceive that the monster under the bed will get us.
In our teenage years, we fear the next steps of our lives and I'd dare say that even the most introverted kid wants to fit in.
In our twenties, we fear being successful or not.
These are gross oversimplifications, but I think the point is illustrated. I think there are two parts to this fear thing. I think we humans are naturally fearful due to thousands of years of biology, and I think we look to leaders out of fear, there's certainly enough evidence of this if you just look at society as a whole and how we behave. Time and time again, societies throughout history look to leaders to placate our fears. The Stanley Milgram experiments touch on this too.
Now for what I perceive to be the dark part of this whole thing. Our leaders have learned that we can be controlled through fear. I say learned, but I possibly mean that this is biological too. If you look back throughout societies, all great societies either were, or eventually became autocratic. We live for someone else to make the scary monsters go away.
Sadly, I think we need fear. Have a look at the Universe 25 experiments to see what happens when a society has all needs met. Spoiler: It appears to end in death and mentally ill behavior.
It's not a leftover, it's a survival mechanism. If fear were stripped away from a person or a society, it wouldn't last long. It's easy to think that rational thought would keep people from dancing on the edge of a cliff but rationality can be undermined through persuasion, self-delusion, and lack of conscious attention. The limbic system evolved as a attempt to keep us safe prior to logical thought and it still does the job.