"Then you'll be able to do it soon."
Link's main focus was on the giant Sandworm's devouring ability. These creatures did not have a stomach, but they ate like a bottomless pit. moreover, with the size of the giant sandworm, it could easily swallow a destroyer, let alone a building.
The premise was that it could be digested.
The giant Sandworm had no choice. It could either agree to Link's request or keep repeating this in the moving Castle.
"Of course, I can't guarantee that my idea will succeed, but no matter what, I will make you stronger!"
Link took out the astral fragment he'd prepared earlier. The giant Sandworm was huge, but its biological form severely limited its development. It could only be underground.
This could be considered Link's bold and imaginative attempt. He was trying to combine materials and creatures that were completely unrelated to each other to see if he could create new sparks.