These groups understand the Republican voters, many of whom are not inclined to rank candidates. Ranked-choice voting favors the more malleable Democrat voters who will do so.
Or in other words, Democrats are more likely to actually think about their votes and find things to appreciate in multiple candidates, while Republicans are more likely to just slavishly vote for whoever has an [R] after their name and disregard everything and everyone else.
And arguably more to the point, Republican politicians count on that.