It’s a bit difficult to say, but perhaps we did in say, maybe through the repetition of flashing images from our memory, or sounds, etc.

Even without language, that internal “making sense” of things / interpreting the world around us still exists - I’d imagine if you were to ask someone who was deaf (starting at a very early age) they’d probably say there is a monologue of some sorts, even if not by “sound”, whether that be the flashing images of various hand signs, or written words, etc.