Billionaires and establishment politicians aren't climate activists. The news sources you hear may be reporting on powerful people, creating the illusion that they speak the most loudly. Activists do speak loudly, do know what they're talking about, and are less likely to be hypocrites, but they don't get reported on.

For facts about the climate, climate scientists themselves would be the primary source (though those of us who aren't scientists will struggle to understand their PhD-level work), followed by science communicators (as they translate for a wide audience the information that scientists learn), followed by activists (who act based on what they learn from science communicators). Billionaires and establishment politicians are in last place.

Climate scientists I follow (as they are also good communicators) include David Ho and Katharine Hayhoe. They're both on Bluesky. Bill McKibben founded the climate activist organization 350.org and has a Substack where he explains things.