Continuity mistake: In the scene where Walter White buys his new car and pulls up the parkway at their house, the wheels are turned when he stops, but in the next close up shot, the wheels are straight forward. (00:02:00)
Factual error: The temporary paper license on the back window of Walt's new car has an expiration of 12 August 2012, the year the episode was released in our time. However, in the Breaking Bad world, it should still be 2009. (00:08:10)
Chosen answer: There are several possibilities. Gus primarily does it to make an example out of Victor. Victor is one of Gus' most loyal henchman, and yet he had no problem killing him. Meaning it doesn't matter how loyal or valuable Walt is, he can still be killed and it won't bother Gus. However, Walt tells Jesse that perhaps Victor "flew too close to the sun." Meaning, Victor over stepped his bounds by learning how to cook meth. Gus didn't appreciate Victor's initiative and Gus only wants his employees to do the job they're given. Again, telling Walt and Jesse to do their job or else.
Bishop73
I think it was a combination of anger over Gayle's death and Victor being seen by witnesses makes Victor very vulnerable and therefore a dangerous liability to Fringe's empire.
By this point, the mugshot of Victor will have been spread around as a suspect in Gail's death. Victor had been come too hot to handle, so to say, so had to go.
Ssiscool