Because people are absolutely idiots. Not a race thing... Most people of all colors and creeds seem incapable of going more than surface deep on anything. I don't know when we dropped our critical thinking skills, but I know it will be the end of us. I think this is what Generations theory sort of predicts. We stop caring about facts, logic, etc. We just drive ourselves into hardship until things are so bad that we realize these things have value . That's my Strauss-Howe pitch of th day. Welcome to the worst part of the seculum.
Lots of 3rd parties are complicit. That's why critical thinking and understanding conscious and unconscious bias is so important. Third parties with agenda are and always will be present. The trick is getting people to understand article by article what is biased or propaganda and how to suss it out. At least the ability to be suspicious without the need to jump to being a full on conspiracy theorist. IDK, it's just so disappointing.
There are most likely more people now with sufficient critical skills than ever before as their existence is predicated on the opportunity for self education. The problem currently is that unbalanced aggregations of personal and corporate wealth are capable of yoking the zeitgeist to their ends so that most untethered minds are functionally insane when it comes to 'political' considerations. It may seem like there are less cognisant minds out there but the reality is that they are being drowned out more than ever by cynical manipulation.
I don't know if the majority of folks really ever had critical thinking skills to begin with. Can you name a time that's notable for most people being rationally critical? I sure can't.