”HIS WAS xxx” 是什麼意思?

For half a century Dr Ian Paisley presented one consistent message to the Protestant people of Ulster. HIS (idea)WAS the lone voice campaigning against the agreement in 1998. So what made Paisley suddenly agree to political compromise?
In English, we always have some "hidden" words such as above. 例:
John is a good tennis player, he is the best (tennis player) in school.

他的
The sentence just doesn't repeat the noun - message
e.g. It's not my idea, it's his (idea).