There is more than one Mandate within Obamacare. The mandate referenced is the one for pre-existing conditions, which was stated in the question. I don’t see a problem with the pre-existing conditions mandate. There are still things that need to be adjusted within healthcare, specifically lawsuits. That would help lower medical costs making it easier to cover pre-existing conditions.
Here is the question that Anderson Cooper asked Trump minus Cooper’s speech stumble where he kept correcting himself in the middle of the question. Here is the question that he asked Trump. “If Obamacare is repealed and there is no mandate for everybody to have insurance...why would an insurance company ensure someone with pre-existing conditions?”
So, Cooper clearly defined the mandate in his question. He defined it as the “mandate for everybody to have insurance.” Doesn’t this make it clear that when Trump said he liked the mandate he was talking about the “mandate for everybody to have insurance”