Why are people so stupid?

let me just say outright what I think, humans are not very smart. an animal wouldn't eat posion, but o wait that is exactly what millions do daily. an animal learns to harmonize with it's enviorment, and what do we do? the governmental system is corrupt, ok I get it, all systems are corrupt right? But why do people simply not care? I see total apathy in these people, likely induced by shitty food and media saturation but idfk. like for instance I have read from various sources that aspartame, artificialasweetenerer is linked with brain cancer, and when I told my family member that they juslaugheded and chugged a diet COKE! lol I know this sounpro ballyly hilarious, but geez its really bothering me lately.