The Vilani Empire was effectively stagnant for many centuries, and technological progress was very conservatively focussed. In many ways, the First Imperium never progressed beyond TL 12 - they never built any jump drive more capable than a Jump-2.

However, the Vilani were interested in improving what they had, rather than in inventing new things. What they had was more reliable, cheaper and more efficient than what either the Second or Third Imperiums could manage at the same tech level. Basically, they could build TL 12 technology as if they were TL 14.