A lot of crappy food survival also depends on individual taste. I worked with a guy from Georgia who always mentioned a one man barbecue joint in his home town as being the best Q on the planet. On a trip to Atlanta wifey and i drove an hour off route to try this famously good pork. To say it sucked was being generous. The meat was hard and dry as wood chips and the "sauce" tasted like it was mostly lacquer thinner and roofing tar with brown sugar and molasses added for a little kick of sweetness. I realized that even though i thought the place should be burned as a public service, the locals apparently liked it enough to patronize the place long enough it was run by the son of the guy who started the place. When i returned to work my co worker asked what i thought of his favorite Q. I told him we got lost and never found the place. To this day when wifey or I taste something horrible we mention that barbecue joint. It has become our standard by which all poopie posing as edible table fare, is judged.I've wondered the same thing.
The conclusion I came to is some of those food trucks are not all that concerned with quality to get repeat customers.
If they can be flashy, have something popular, they can draw in people over and over who want to try it out. It ends up being not so good, but there are some folks who will try it again thinking maybe that was just a one time deal. They try again, and realize it's just bad and stop going.
That approach won't work everywhere, but in areas with high traffic and turnover of people, the business from repeat customers is probably not that big a deal.
-Mike