Hm, if you don't remember the problem causing the switch, how do you know it was the switch itself that improved the situation?
Naming the 'why' behind the emotions is a job for 12+ year old, not for the kindergartener.
An important part of the human developmental process is learning to calibrate these sorts of things, and one way to calibrate one's reactions is to have adults check whether the child's intuition about something was correct or not.
There can be some cases e.g. hidden abuse where the adult thinks the child may be being unreasonable where they are not, but in situations where the child and adult have equal information it's a valuable learning tool.