why big businessman or rich person open trust

To help needy thru their Trust.

Regarding the link shared, how are these people "big" ?

I didnt even know them and so does google. 

Turn black money to white money 💰 🤑

Not sure how many people really end up helping the needy with their trusts. A lot of these rich guys are narcissists and want to be portrayed as some kind of philanthropic person - just look at the wikipedia entry of every rich person and you'll see they have been edited to describe themselves as philanthropist. It ultimately helps them with tax exemptions and to pass on their money to the next generation.

These are general benefits , this is just tip of the iceberg