Alien Runner uses deductive reasoning to reach theories and conclusions.
The Prometheus movie shows us that the black goo deconstructs DNA structure to create new life.
David drops black goo on Engineers.
What happened when Fifield ingested the black goo? He turned into a humanoid alien looking creature.
The black goo reverse engineered Fifield Human's DNA into an alien creature.
Guess what? The black goo does the same with the Engineer. Well, in the case of the intro in Prometheus, the Engineer regressed into a primitive human being after ingesting the black goo. David probably accelerated the regression process from Engineer to Human to XENOMORPH. He saw the Mural. He realized that the Engineers were worshiping their ancient ancestor, the Ultramorph.
It all comes full circle. David is playing god. He is going to be god by surpassing the Engineers and in order to do that, he needs their power. But how can he control them? The only way is to regress them into their primitive state, which are the Xenomorphs. With that under his control, he can destroy Humanity and carry out the Will of Engineers.
Talking about yourself in the third person is quite annoying and arrogant, but let's get to the subject at hand, shall we?
First of all, the black goo MO is all over the place, starting with the worms, them Fifield, then Holloway/Shaw 'spawn', then finally the Engineers in Paradise... The latter were petrified, they did not become bigger (like the worms) nor more distorted and feral like Fifield... They were just killed instantly, as their statuesque bodies attest... They did not become distorted monsters tearing eachother out nor increased in size... They were just killed instantly... You do not die on your feet when you are killed, you fall and die... These Engineers bodies were petrified while standing, crawling... Fifield fell on the black goo and did not petrify... Ridley keeps changing the goo's properties as a deus ex machina ploy, as a convenient narrative placeholder...