A lot of them either didn't think he'd really do it, or had no idea what a "repeal and replace" would look like.  This reminds me of the late night show that was asking people on the street what they thought of the Affordable Care Act and ObamaCare.  It was shocking how many people hated ObamaCare, but loved the ACA, having no idea they are literally synonyms for each other. They only liked it if Obama's name wasn't attached to it.