i would quickly answer: because the work and end goals of progressivism are exactly opposed by the Constitution and founding of this country, there have always been a small remnant of the political class in this country through the 20th century who were true constitutionalists, and we had some true conservatives (republican in name only in a good way) as presidents (i can think of three) interspersed with all the leftists.
you said they were the same then why didn’t r’s pass all that if they were the same as d’s and wanted to destroy America like dems do?