In the next 15 years, more than one in 10 colon cancers and nearly one quarter of rectal cancers will be diagnosed in patients ages 20-34, according to the study. It also found that, in this age group, colon and rectal cancers are expected to increase by 90% and 124.2%, respectively, by 2030. For those ages 35-49, the predicted increase will be 27.7% for colon cancer and 46% for rectal cancer. Routine screening currently is not recommended for those under 50.

https://www.mdanderson.org/publications/conquest/colorectal-...

Also, if you have a family history of colorectal cancer, you should definitely get examined earlier.

Do we know the cause of this? More consumption of red meats?

I've seen a study that points in that direction, but I don't think that's conclusive.