It's the same with F1 - To the untrained average person the entire grid of F1 cars probably looks identical but with different colours, yet one will be 3-5 seconds a lap faster then another, so tiny differences = big differences on track.
You could also argue that the Cat 3000 was the first with this layout, and actually the Losi XX4 was the first 4wd competitive car to have a motor anywhere near the front of the car, this was a massive difference to previous 4wd off road cars but is almost the norm now!
Things change and improve all the time as the years go by, it's called Evolution
We're at the stage where these cars are all so good now, it's only small changes that are being made to gain every last 1/10th of a second. If you look at for instance the first Losi JRX, then the XX, XXCR, then the XXX, BK2, CR - They're fundamentally the same "design / layout" but with Geometry and slight weight distribution changes over the years hence Evolving into the current XXXCR that people are running today.