The ESA seems like it should have been an incredibly divisive piece of legislation at the time, and yet it was strongly supported by Nixon and passed the House and Senate with votes of 390-12 and 92-0 respectively. What forces, political or otherwise were at play here? Was the environmental situation just that dire, or was there more to it?
The endangered species act was a by-products of the drive for conservation in the 1900, as a result of the disappearance of several species such as the bison. In addition, the concept of the extinction of animals began to gain support with articles being published on the new concept of extinction. Before the act was passed the Endangered Species Preservation Act of 1966 was passed which hoped to protect endangered animals. Further research though found that the act and the list of the endangered animals wasn't doing enough to protect these animals which led to the endangered species act obtaining more power. Just a short summary.
Wilcove, David S. et al. The Endangered Species Act at Thirty.