Thumma normally indicates delay, but the textbook also illustrates a use akin to waw’s joining function. In the cited verse, faith is joined to the related qualities without requiring a conclusion that faith chronologically began only after every other action.
«ثم كان من الذين آمنوا»
And he was among those who believed.
The excerpt from Surat al-Balad 90:17 serves as a contextual example: sometimes conjunction is the operative meaning instead of literal chronological delay.
It would therefore be unsound to impose an actual interval on every occurrence of thumma regardless of context.