They didn't. If they did then there would be evidence of their stellar and galatic level engineering visible even today. Once you get to a mature interstellar culture the species becomes impossible to erdicate. Some trace of it will ALWAYS survive.
Multiply that existence across deep time and something should have generated some kind of ultra-engineering visible at interstellar distances.
The answer is obvious. We are just not advanced enough yet to see what they have done.
Have you ever considered that we are an artifact of some advanced civilization?
We don’t even know what gravity is yet. We are primitive beyond description compared to a race a million years ahead of us.
John