The gap between GOP voters who want John Bolton to testify (70%) and GOP senators who want witnesses (somewhere between zero and 4/51) can be completely explained once you consider that GOP voters think Trump is innocent because they believe the Fox news version of events and GOP senators know he is guilty because they actually know the actual truth.
This also explains why right wing media has turned on Bolton.
“New poll says 82% of all Americans want John Bolton to testify for Trump’s removal trial, including 70% of Republicans,” Scott Dworkin, co-founder of the Democratic Coalition, tweeted Wednesday morning, using the trending hashtag. “So the GOP Senators have a choice to make. They can side with the American people, or they can be traitors for life and side with Trump.”