One of the things that conservatives like to obsess about is why liberals are liberal. The two most common explanations are referenced in the title, but sometimes I think that there's a third explanation. At least in the US, I think that liberals are liberal because they are instinctively conservative, in the sense of being content with the status quo. If you're content with the status quo and the status quo is liberal, then you end up being liberal.
That's why my conservatism isn't much shaken by the big questions status quo conservatism got wrong, which in the US are basically slavery, Jim Crow and civil rights. Status quo conservatism is too prone to the position that some practice is unfair/unjust/oppressive, but now's not the time to rock the boat. Once you've taken that position, it's never time to rock the boat. The right position is that it's always time to rock the boat, if the cause is worth risking upsetting the boat entirely. That's why, for the past 30 years, our reactionaries have been liberals and our radicals have been (non-status quo) conservatives.