>I lean toward "people got better at not dying from everything else."

Unfortunately, that doesn't seem the be the case here, and the article goes into this. Deaths due to colorectal cancer under 50 simply used to be incredibly uncommon. Younger people were simply not screened for it. The rise is not solely relative to other forms of death, but in absolute terms has increased.

There could still be another factor other than lifestyle or chemicals in the food, the dominant opinions as of posting. Point (which I realize I forgot to make) is we don't know and latching on to pet theories, even really smart ones, has never done anyone any good in general, but especially when it comes to health.