Why do people eat food they know isn’t good for their health? Why do people continue to buy products from companies that have proven to only sell bad products or engage in scumbag practices?

They all have the same answer.

Each individual is facing the following choice in life:

• sacrifice to save the planet, and fail
• or not

People want to immediately jump to “if everyone would just …”

Nobody is looking at an “everyone does X” button. People only have their “I do X” button available.

So that is literally the answer to your question. Very few people would sacrifice the civilization to eat a cheeseburger. But nobody has that choice or that power in their hands. Their choice is eat the cheeseburger or not, and the survival of civilization stays rigidly the same between those two choices.