Origins
Something obvious is standing in the middle of the road. The word comes from Latin obvius, composed of ob- ('in the way of') and via ('road, path'). An obvious thing was not merely visible — it was blocking your route. You had no choice but to encounter it.
The Latin via produced an entire vocabulary of movement and paths. Voyage is a journey along a road. Deviate means to leave the road. Convey means to travel with (originally to escort someone along the way). Previous means going before on the road. Obviate means to clear the way — to remove the obstacle.
Trivial belongs to the same family, and its etymology is equally spatial. Latin trivium meant 'three roads' — a crossroads. These were places where common people met and exchanged everyday knowledge. Trivial information was crossroads gossip: common, widely known, not worth a scholar's time.
Figurative Development
The shift from 'physically blocking the path' to 'intellectually unmissable' happened without any strain. The metaphor maps perfectly: what blocks your road cannot be avoided; what is intellectually obvious cannot be denied.
Obvious entered English in the 16th century, later than many Latin borrowings, perhaps because English already had plain, clear, and evident. But obvious carried something the others lacked — that image of an unavoidable obstacle, something so present it stands between you and wherever you were going.