It's many reasons - some of it being fear, some of it being disinterest in anything that doesn't concern a person's immediate well-being and family, some of it being group-think and social acceptability and belonging to a certain social-circle, some of it being racist and colonial ideologies, and many more reasons...
One important reason (IMO) is the lack of critical thinking in society - i.e. the lack of skills to parse through the propaganda that you mention - the lack of logical and reasoning abilities to separate fact from fiction, narratives from reality.
It's many reasons - some of it being fear, some of it being disinterest in anything that doesn't concern a person's immediate well-being and family, some of it being group-think and social acceptability and belonging to a certain social-circle, some of it being racist and colonial ideologies, and many more reasons...
One important reason (IMO) is the lack of critical thinking in society - i.e. the lack of skills to parse through the propaganda that you mention - the lack of logical and reasoning abilities to separate fact from fiction, narratives from reality.