With a few notable exceptions (such as Ted Cruz), when these "conservatives" we elect get to Washington they either go back on what they said they would do for conservatives and conservativism (i.e., they lie), or they say that despite the promises they made during the campaign there's really nothing they can do about anything.
So I agree that although Trump's conservative bona fides are, at best, an "unknown", the antipathy toward conservatives and conservatism of the other realistically viable candidates (again, with the exception of Cruz) is very well known -- and despised -- by conservatives, which is why this conservative will take my chances with the "unknown" Trump over the lazy, duplicitious "conservatives" which are the alternative.
As opposed to the notable exception that you cited multiple times in your response? No offense but that makes no sense