だけに: a circumstance that intensifies a feeling or result
Read how expectations, relationships, or circumstances strengthen a following feeling or effect. Check positive and negative results and the circumstance receiving emphasis.
Greater disappointment because of anticipation
楽しみにしていただけに、中止の知らせは残念でした。 means that anticipation made the cancellation especially disappointing. The prior expectation explains the intensity of the disappointment.
Cancellation is not presented as fitting the expectation. Even when the facts point in opposite directions, だけに works if the first circumstance explains the strength of the following feeling.
A reason for joy or special care too
長く待っただけに、合格の知らせはうれしかったです。 says that the long wait made news of passing especially welcome. Do not restrict だけに to disappointment or negative outcomes.
大切な資料だけに、扱いには注意が必要です。 means that because the materials are important, they need careful handling. The expression can emphasize a reason for special care as well as a feeling.
Connections and comparison with だけあって
Nouns connect as 初めての仕事だけに, na-adjectives as 複雑なだけに, and verbs as 待っただけに. Check the final predicate to establish whether the result is past or present.
経験者だけあって、判断が早いです。 evaluates quick judgment as fitting experience. 経験者だけに、今回の失敗は意外でした。 instead says that being experienced made this failure especially surprising.
Quick check: Does 大切な友達だけに、本当のことを話したいです。 say that the whole truth has already been told?
Show the answer and why
No. It expresses a wish to tell the truth precisely because the person is a dear friend. 話したい is a desire, not a completed act of speaking.