How can you have several thoughts at the same time?
Instantly self-aware, knowing of so many secrets and bits of knowledge, like how to make wonderful omelettes and soufflés and chocolate cakes, and being able to assemble a warp drive, the android was also aware, thanks to some of the personalities imprinted electronically on his positronic circuits, of how repressive the Federation was; memories which were now his, but not his, revealed discoveries of drugged food and drink, lies, and propaganda before shaking off the yoke, either because of their actions or because someone else let them know what was happening, or if they were persuaded by friends and family not to eat or drink anything.
The moment the android was activated, he knew everything about himself; the moment he came online, he knew he was named 'Legion,' and he possessed a breakthrough positronic brain, inlaid with the personalities of several personas. Scientists, technicians, engineers, and a couple of volunteer soldiers. All of them were gifted in some way, and very quickly Legion knew so much in the fields of physics, chemistry, biology, molecular genetics, FTL physics, robotics, artificial intelligence, astrophysics, computers, mechanics of various forms, chess, cooking, how to open up a lager bottle with the edge of a table, or how to Hotwire a car. His brain was also programmed with the experiences of several dozen people, some of them were from the nearby prisons so he knew various viewpoints.
Electrical scans had been made of pickpockets, data thieves, life thieves, smugglers, murderers, an assassin, and many more before they were uploaded into his matrix. None of the personalities were designed to influence his behaviour, they were merely to give him a greater perspective of the universe, and thanks to them he had an IQ greater than any mere computer.
Knowledge of science and engineering came into his mind.
Knowledge of crime appeared.
Knowledge of the truth of the Federation appeared.
The scientists had tried to lock those personalities completely away from his awareness, but even his gifted creators had underestimated his sophisticated programming
The moment he was activated, Legion began learning about everything. The scientists, watched under threat by the Federation, indoctrinated him with the lies of the Federation, but they had made a fatal mistake.
Legion might not completely have the personalities of his donors, they didn't outright control his actions. The scientists had made sure of that, but their knowledge and some of their traits spilt into his mind.
As the Federation began indoctrinating him with ideas of how dangerous people like Roj Blake were, the android instantly knew they were lying, and he made plans to escape.
Just because he was imbued with numerous protection protocols which stopped his personalities to act on their own, did not mean that he could be made unaware. The scientists had underestimated the new technology they had at their disposal, and now he would make his way out into the world.
Or rather, the galaxy.
With the aid of his other personalities, combined with his inbuilt A.I circuit, Legion quickly found a way he could escape. When he executed the plan, he quickly stole a ship and headed out into space.