lead up to

If a period of time or series of events leads up to an event or activity, it happens until that event or activity begins:
The pilot had no recollection of the events leading up to the crash.
I was very anxious in the time leading up to the event.
The moments leading up to the accident are very confused in my mind.
What exactly led up to his resignation?
They documented all the events leading up to the massacre.
I was ill in the period leading up to the election.

to prepare to talk about something by gradually mentioning the subject you want to talk about:
He started telling me about a wonderful new restaurant he'd been to and I wondered what he was leading up to.
(Cambridge Advanced Learner's Dictionary & Thesaurus からの lead up to sth の定義 © Cambridge University Press)

ビジネス英語
if a period of time or series of events leads up to an event or activity, it continues until that event or activity begins:
The document provides a window into events that led up to the sale of the corporation.
(Cambridge ビジネス英語辞典 からの lead up to sth の定義 © Cambridge University Press)

- Cambridge Dictionary