Fëanor was more often than not single-mindedly and selfishly intent on anything that he was currently occupied with. The Silmarils were just his last and greatest achievement. Rarely were his hands idle in those days. His mind even less often so. Always devising new things, new ideas, new inventions.

So the forced idleness that the stay in the Halls entailed was bound to make a dent. To leave a mark even on his insatiable spirit. To change him, even if he denied it, in ways that have never occurred to him before. It pushed him to do one thing he never cared about doing. To stop and think about what he has done, and why. He had no other choice there. Being presented with the incessant flood of images, the consequences of his decisions in all their gory detail. It made him reflect on his decisions and choices. To come to the conclusions, on his own accord, that many of those were not his greatest moments.

Fëanor would rather be caught dead than admit it but it was this new habit that he acquired there, without even know that he did, what made him go down the empty streets and into the buildings in search of more people they could escort out.

Killing goblins was easy. Going back for those people was not.