So what? Vegetation diet 100 million years ago I'll guess that obesity is nill comparatively to today.
I'll also guess that there was comparatively virtually no obesity in the Paleolithic period.
Nowadays we live in a period where we're told pasta is healthy, or orange juice is healthy (a lot of brands have more sugar in the juice than coca cola). We all eat lots of bred, refined carbs. Sugar has never been so readily available. Parents buy their children sweets all the time.
And guess what? We're turning into a developed world of obese people and higher levels of heart disease.
So yes, a modern vegetarian diet probably is healthier and safer than sandwiches, crisps and orange juice.
Paleo diets are not fads. Our bodies are tuned to metabolise those sorts of foods. People relentlessly defend carbohydrates when they are the most likely candidate for the epic levels of obesity and other related diseases.