Many on the professional Right owe their livelihoods to a large and growing network of nonprofit donor-funded groups and for-profit consulting and direct marketing companies hired by those groups.
There are a lot of people whose livelihoods depend on keeping lots of conservatives terrified and ill-informed. The groups that exist to raise funds raise more funds when they endorse the crazier candidate.
American politicians are responsive almost solely to the interests and desires of their rich constituents and interest groups that primarily represent big business.