The answer: They did right in one go because they did a LOT of testing, and by using proven designs.

Also:

A precoded message from Blue Ghost marked the moment Sunday afternoon, signaling a transition to “monument mode.”

“Goodnight friends,” Blue Ghost radioed Firefly’s mission control center in Central Texas. “After exchanging our final bits of data, I will hold vigil in this spot in Mare Crisium to watch humanity’s continued journey to the stars. Here, I will outlast your mightiest rivers, your tallest mountains, and perhaps even your species as we know it.”