Many conservative American Catholics are conservative Americans first and Catholics second, and that shows up big time in their views on subjects like this due to the past thirty or forty years of political alliance with Evangelicals.
To be honest most of them have simply never had the Church's position explained to them coherently. And on top of that the Church does not require us to believe in evolution, so there's not a huge point in raging on about it. You are vastly overestimating the malice of the normies here; most of them just go with the flow, and since the religious culture of the US is driven by evangelicals, a bunch of Catholics are going to end up thinking evolution's not real.
