For two years, Carl has been costly observing the territory of Crimson Claw to make bases and prepare for an all-out attack.
Naturally, during those two years, he formed several hideouts around the mainland and one of those bases can be used by Richard and his people for the time being.
The place Carl brought them was an underground facility which can only be reached if someone knows the exact location of the hideout. In the middle of nowhere, there is a secret passage that opens up under the plain ground, and the gallery leads to the hideout.
Seeing Carl inputting the third password in this five-minute walk, Bella couldn't help but think,
'Paranoia or just caution?' She couldn't comprehend how much grief and regret he must have gone through. Sharing one's pain and experiencing it, are two different things.
Bella or anyone else can assure him of the future and comfort him about the past, but the suffering he went through can never be erased.