It's fuckery, they are saying will not take AND unsure. The trend line down likely comes from the "unsure" aspect which has turned into either yes or no for a vast majority of people by now. This can be exepmlified by the upward spike of "white republicans" in the beginning of vacinations because, on the whole, that group is more likely to be wary of the government and research.

This entire chart is designed to 1) divide people into groups and 2) direct hate of the other groups toward the group(s) that the interested parties want to destroy. They are trying to use societal pressure to beat "white republicans" back into the silent majority to pair with the narrative they created with Biden's BS "epic win."

Sadly, know all this information has made this movie somewhat boring. It's the same damn playbook every time.