Choice. Sydney never guessed it, but it was all a matter of choice. Sark knew the CIA and Sydney were constantly analyzing him and his actions. He could imagine their comments about how he came to be:
"Must have been an orphan."
"Parents didn't show affection."
"Programmed by the KGB."
"Irina brainwashed him."
"Irina was around---need we say more?"
It amused him. Sometimes Sark thought that Sydney tried to see the good in him. Good luck.
Was she trying to convert him? Doubtful, because she admitted that she saw him as a cold-blooded killer and monster. But she still wondered about him.
And how could she not? Sark was very aware of how hot women found him. Add that together with his natural charm, and Sydney was thinking about him in her sleep. She never admitted that, but Sark knew. He could see it in her eyes whenever they met.
In addition to imagining him in her mind, Sydney was wondering how he came to be so "bad." All those excuses and theories she and the CIA created were nowhere near the truth.
Sark had parents and quite the ordinary family life. He played soccer when he was young with all the neighborhood kids. He chased girls around the playground like 9-year-old boys are supposed to do. He had dinner every night, even homecooked meals by his mom.
Once a year the family took a trip to London or to Scotland or whatever place that was designated the European hotspot. Growing up was fine---normal. His parents were still alive and so were his siblings. Irina never sought him out. It was the other way around.
And why? Simple. He chose to leave normalcy. It was boring. It was cheesy. It was unreal to him. He wanted more. So he faked his death and changed who he was. He ditched his Irish accent and adopted English. He styled himself in whatever way worked to his advantage.
Some might call his life less as it was now, not more, but he found it exactly as he made it. What he wanted, he obtained. After a bit of research, he learned of Irina. He "interviewed" for a job under her direction. And he advanced from there. It was choice.
Sydney could never understand why, but he chose to be Sark. The assassin. The resourceful spy. The charming man in the shadows. Her opponent. This way, he was in control. His life was determined by himself and his actions. His choices.
And in order to get closer to her, Sark would accommodate Sydney's theories and sympathetic assumptions. Anything to win her.