They heard Walz appointed the guy to some small time advisory commission, almost ceremonial only in impact. So they thought Aha! He and the Democrat are big pals. Then they read that one of the victims, a D, had voted against the Democrats to block immigrants from accessing health care and they all said Aha! he's knocking Ds off who didn't toe the line. Then the photocopied No Kings sheets confirmed it for them. Aha! a marxist looney! They knew it from the beginning!
But it came out that 1) He had last voted in a Republican primary (not Democratic), 2) He said a bunch of pro-tRump things to his roommate, 3) all the hit list targets were all pro-choice, 4) all were Democrats, and 5) He was anti-progressive (example anti-LGBT) pastor in his own evangelical church movement and gave right-wing aligned sermons on video tape.
But their narrative was set and most maga were saying for more than a day the media is pulling a fast one and lying by calling him pro-tRump.
I just looked now and it seems they have finally changed their tune and aren't claiming he is left or Democratic any more.