How could science be manipulated?

Don’t get me wrong, I’m a believer of science. I have a lot of science books lying around my rooms.

But there seems to be a time in history when bad people tried to use science to manipulate the public. I remember at one point tobacco companies hired scientists to come up with “results” that claimed tobacco had no harmful effect to the body. There are also similar incidents throughout history.

So my question is, how could anyone manipulate research results, if science is the truth? Did those scientists make up random statistics and just slap their names on it?