The optimal strategy in this case is to expand as quickly as possible, before others can grab or destroy resources.
seems like an odd thing to claim, given that we have no idea what's going on on any planet outside of our solar system
Still makes no sense.
So yeah, a lot of prime real state but no way to reach it.
This subplot in the book is at least reasonable. Somehow aliens capable of pico-scale engineering can't make a telescope to observe the nearby solar systems, but OK, whatever. Cultural blindness and all that.
It's the later plot with the "dark forest" that makes no sense. There are ships capable of moving at relativistic velocities and spacetime-altering weapons.
Barring some magical woo-woo technology that someone will probably insist must exist because we foolish humans are simply too stupid to understand anything, this isn't something you can just cheat. There ain't no stealth in space[0].
https://www.projectrho.com/public_html/rocket/spacewardetect...
The first book is Off Armageddon Reef - https://en.wikipedia.org/wiki/Off_Armageddon_Reef
In the 24th century, 8 million people flee to distant Safehold after barely escaping from the destruction of civilization by a genocidal alien foe, the Gbaba. Because the enemy tracked signs of advanced technology to hunt down other emergency colonies, the plan is to enforce a pre-industrial society until the danger passes. Administrator Eric Langhorne, a megalomaniac and neo-Luddite, instead has the colonists' memories erased and replaced with the belief they are the first humans, "Adams" and "Eves," the creations of God upon Safehold with "Archangel Langhorne" anointed as prophet and leader of the Church of God Awaiting.