I thought all those studies have ppl eating processed meat along with industrial junk food. Its hard to eat vegetarian food like that.

Is it just purely correlation ?

Most vegetarians I know eat tons of heavily processed frankenfoods meant to mimick popular non-vegetarian foods. They also tend to eat lots of sugar and simple grains. The biggest exception has been my Indian coworkers, who tend to either make or source vegetarian meals that respect that vegetable is the root word in vegetarian.

Correlation doesn't imply causation.

People picking a vegetarian diet (which has been the mainstream healthy option for the last 50 years) are probably more health conscious than someone downing 5 mcdonalds per day.