I would agree there are plenty of celebrities preaching about things like climate change that are massive hypocrites and emit more CO2 in a week than I do in my life. However I think you have a weird view of who these scientists are. They aren't billionaires, they're everyday people for the most part and are concerned when their expertise shows worrying predictions of the future.

Creating peer reviewed papers that warm of climate change and its impacts isn't fear mongering, it is their job. What the media and people do with it is fear mongering but science isnt. I think you vastly overestimate the influence scientists have on things like public policy. Lobbyists for companies have orders of magnitude more influence on policy across every industry than the people doing research.