The Sith's two tools, the Wayfinder, which the Emperor and Lord Vader had, are in the remains of Exegol and Deathstar. It is not a simple composition that Len gets one, Ray gets another, and aims at Palpatine.
Only Len knew about the wayfinder. Did Len use the intelligence of Palpatine's rumors and the intelligence of the Empire? It is certain that Palpatine was inviting Len behind. So I could easily find Exegol. Len can contact Palpatine ahead of Rey,
but the wayfinder has not been destroyed, although it has been used up.
Meanwhile, Ray finally gets another wayfinder between the thrones, but is broken by Len. This is a relieved Len, but the whole ship is robbed by Ray while leaving the way finder that was not destroyed in the Thai silencer lol
Interestingly, Rei did not realize that the wayfinder was on board. Rei stops at Okto and, as Luke advises, finds the wayfinder on board!
The ISD fleet in Exegol was the last resort hidden by the emperor and Vader. As a weapon when the empire is about to break apart in a civil war or wants to pass legislation like emergency power again. It's fun to imagine that Vader advised the emperor to hide his fleet in Exegol. However, after all, the emperor would have planned to use it for the revival of the final order. It seems that General Pride is involved in the process.
I feel like the wayfinder stores secret information in addition to the exegol coordinates. When the Emperor comes to the Death Star, it's important to bring it with him. It was important not to leave it in the strictly guarded Coruscant Palace. I feel like Mustafar's Vader has been thoroughly managed. If the Emperor himself died, he would have taken measures to recover it, or if Vader died, to a new disciple.
It is more valuable than the holocron in the Coruscant Jedi Archive.