This is the 11261st most frequent Turkish word.
düşünmüştü
"Had thought."
The usage of 'düşünmüştü' here reflects the action of thinking repetitively or habitually, completed prior to another moment in the past.
O, eski günlerde yaşadıklarını sıkça düşünmüştü.
He often had thought about his experiences in the old days.
Although 'düşüntü' here is describing a specific thought completed in the past, its use structurally sets the stage for subsequent action.
Projenin başarıya ulaşacağını düşündükten sonra harekete geçti.
After he had thought that the project would succeed, he took action.
The word 'düşünmüştü' is the past perfect form of the verb 'düşünmek', meaning 'to think', indicating that Ahmet had completed the act of thinking about this matter before another point in the past.