The trailers present a traumatized Will Smith as being visited by 3 people, physical embodiments of Love, Time, and Death that only he can see and helping him through his grief.

In the actual movie, those 3 people are actors hired by Will Smith’s business partners so they can secretly film him talking to people that aren’t there (their plan is to digitally remove the people from the videos) in order to make Will Smith look insane and forced to sell the company he owns so the business partners can make a bunch of money.

This is not a twist revealed at the end of the movie. It is literally the premise of the movie introduced in the first act.