It's not that all obvious to me. Where I live the richest don't get this kind of attention very much. People know they're the richest and all that but you don't see their opinions broadcasted on every social media and news outlet. On the contrary, they're mostly out of sight, out of mind!
Because they aren't buying newspapers. American rich people don't all have the common sense to just be rich and enjoy their opulent life discretely, they need to also insert themselves into the national dialogue.
The US has never had a situation where the rule of law collapsed, and mobs were actively trying to kill the elite. ("Elite" here meaning those with extreme amounts of money or social status.) In places like Europe, they remember things like that.
So if you're an elite there, you don't make waves or have a high profile, because you know from history that doing so can attract attention of a kind that you really don't want.
But in the US, that's not in your history. So, especially if you're rather narcissistic, you think of using your wealth to get attention.
