Through television broadcasting many people had known about the president’s vision and mission.
Even without looking at the surrounding text, it’s extremely unlikely that past perfect tense was the right choice here.
Actually there are very few situations in IELTS writing where past perfect is appropriate. The only time you might need it in the writing test is in Task 1. I deal with this in another post: past perfect in Task 1 writing.
Past perfect is used mostly in narrative when the writer wants to introduce events in non-chronological order, for example when certain events are for some reason more important than other events.
Most of the time past simple tense is all I need to recount a series of events in the past:
On the other hand, if someone asked me “When did you go to the post office?” then I might reply:
The chronology is the same – bank, then post office – but I was asked specifically about post office, and so I mentioned post office first.
Again, this re-ordering of events is almost never necessary in IELTS writing, and seldom used in speaking. Indonesian students over-use past perfect tense and rarely use it appropriately. My advice would be to stop using it altogether, at least in the IELTS test!
For my next post I’m planning a listening activity to focus on the sequencing of events in narratives. Stay tuned!