This is not surprising at all, if anything it's surprising that it's not higher. First, it is the Democrats mantra, and their willing accomplishes (the media) are pushing it as well. Most people do not understand of the Constitutional explict roles between the House and the Senate and they believe that this can be brushed aside so that the Senate can launch it's own inquiry. Since that is what they know about what goes on in courts, they want to see another episode of Perry Mason or Court TV. Just like they see on TV, they think that the Senate can resolve the mess that the House produced, discover the truth, and deliver a fair result.
This is what the Democrats want, it's the only way that they can recover from this disaster, and the Trump defense wants to put an end to this nightmare. Politicians will want to get both. We have a small chance of keeping the Republican puppies in the box, but it will be close. Pray for our Republic.
I have read several articles about the Impeachment issue, McConnel, Bolton, and others. IN the Comment sections where the witness testimony issue is raised, the like/dislike voting always is about 3 to 1 in favor of testimony. Often it will be like 250 to 70 or similar.