をきっかけに: the event that starts a change
Distinguish presenting an event as a starting point from simply explaining a reason.
A starting point for an action or change
をきっかけに presents an event or experience as the occasion that starts a new action or change. 留学をきっかけに、異文化への関心が深まりました。 means that studying abroad sparked a deeper interest in other cultures.
It does not establish that there was no interest at all before studying abroad. 深まった can describe an existing interest becoming deeper, so do not confuse the emergence of a catalyst with the absence of any earlier interest.
Use a noun or turn an event into a noun phrase
転職をきっかけに、生活のリズムを見直しました。 means that changing jobs prompted the speaker to reconsider their daily routine. をきっかけに follows an event noun such as 転職 directly.
To express the event with a verb, nominalize it with の, as in 友人に誘われたのをきっかけに. 友人に誘われたのをきっかけに、写真を始めました。 means that an invitation from a friend prompted the speaker to take up photography.
A starting point, not every aspect of causation
雨が降ったので、試合が中止になりました。 gives rain as the reason a game was canceled. For a straightforward cause and result, ので is natural here; not every reason needs to be expressed with をきっかけに.
In a sentence about a catalyst, look for what began to change. The expression does not claim that the event was the only cause or a deliberate objective. A chance experience can also become a starting point.
Does 留学をきっかけに、異文化への関心が深まりました。 mean there was no interest in other cultures before studying abroad?
Show the answer and why
No such conclusion follows. Studying abroad was the occasion for that interest to deepen. 深まった can also describe an increase in an existing interest.