We are swiftly moving to thoroughly reject the "Reality-based Community"[1] of facts and expertise that (reportedly) Karl Rove dunked on 20 years ago:

    The aide said that guys like me were 'in what we call the reality-based community,' which he defined as people who 'believe that solutions emerge from your judicious study of discernible reality.' [...] 'That's not the way the world really works anymore,' he continued. 'We're an empire now, and when we act, we create our own reality. And while you're studying that reality—judiciously, as you will—we'll act again, creating other new realities, which you can study too, and that's how things will sort out. We're history's actors...and you, all of you, will be left to just study what we do'.

1: https://en.wikipedia.org/wiki/Reality-based_community

I think the rise of C-SPAN was also a factor.

Once all congressional speeches began to be televised, everything started to become campaign fodder. Members of Congress were no longer talking to each other, but always and endlessly trying to appeal to the voters.

Congressional hearings are even worse. Very few congresspeople seem to have any interest and asking meaningful questions. They seem to be focused on getting a video snippet that proves how hard the are fighting for/against a particular issue.

It's all become an endless political campaign. Evidence has never mattered too much in those.

Of course, it's good to keep in mind that what politicians say in public speeches doesn't necessarily reflect how they reason internally, just what they think will be most effective to get the desired result from their current audience. There's also the factor of current stylistic trends among the congressional staffers who write speeches and briefing outlines.