本来 has two key uses: (1) as an adverb meaning 'originally, at first,' stressing a past situation that later changed; (2) as an adjective meaning 'original, former.' Unlike 原来 (yuán lái), which can also express discovery ('so it's you'), 本来 never carries that 'turns out' sense. In the pattern '本来就…' it means 'it goes without saying' or 'of course' — stronger and more presuppositional than 当然 (dāng rán), emphasizing that something was already the case.