hobbyhorse vs preoccupation

hobbyhorse and preoccupation both are nouns.

Word	Noun	Adjective	Verb	Adverb
hobbyhorse	Yes	No	No	No
preoccupation	Yes	No	No	No

As nouns, preoccupation is a hypernym of hobbyhorse; that is, preoccupation is a word with a broader meaning than hobbyhorse:

hobbyhorse (noun)	preoccupation (noun)
a child's plaything consisting of an imitation horse mounted on rockers; the child straddles it and pretends to ride	the act of taking occupancy before someone else does
a topic to which one constantly reverts	the mental state of being preoccupied by something
	an idea that preoccupies the mind and holds the attention