Politics mixed in with man-made global warming way back before it had much scientific support. It is only as big as it is now because the politicians and environmental organizations have been pushing it, and have been providing most of the paychecks for the scientists studying it to that end. The likes of Al Gore are anathema to science. All of this is why I distrust man-made global warming.
Evolution has quite a different history, as do most areas of science. Evolution started as the underdog by a disinterested scientist (Darwin was very religious at the time), and it was subject to claims of heresy. Despite this, after decades the evidence built and it became more and more accepted, eventually becoming the dominant scientific theory on its own merits.
Even with Piltdown man scientists were skeptical, and they eventually disproved it. Same for Nebraska Man as I mentioned. Archeoraptor didn't last long before evolutionary scientists shot it down, and the Cardiff Giant was flat-out dismissed. They have policed themselves well.