収まる: rain subsiding and all the luggage fitting
Compare heavy rain subsiding by nightfall with all the luggage fitting on a shelf after organization, retaining both reported results.
Reduced intensity and a fit within a space
収まる (おさまる) describes subsiding rain and luggage fitting in these two scenes. Distinguish the reduction of a strong state from objects fitting into a stated space.
For the rain, identify the change in intensity and the nightfall timing. For the luggage, identify everything that fit after organization and the shelf that held it. Both sentences report results.
The nightfall change and the storage result
「激しかった雨は夜になると収まった。」 (The heavy rain subsided by nightfall.) The heavy rain subsided by nightfall. Its intensity eased; the sentence does not establish that the rain stopped completely.
「荷物を整理したら全部が棚に収まった。」 (After organizing the luggage, everything fit on the shelf.) All the luggage actually fit on the shelf after it was organized. 全部 retains the scope of all the luggage. This is a completed fit rather than a mere possibility, and no enlargement of the shelf is described.
Track the subject of each changed state
雨は収まった concerns the rain's subsiding state. 全部が棚に収まった concerns all the luggage fitting. 棚に identifies the storage space without naming an object whose size was changed.
The luggage sentence connects 整理したら with the result 収まった. Retain the organization and the actual fit, keeping this storage result distinct from the change in the rain's intensity.
Does all the luggage fitting on the shelf mean the shelf was enlarged?
Show the answer and why
The sentence reports that all the luggage fit after it was organized. It describes no enlargement of the shelf and presents an actual storage result rather than only a possibility.