(I feel really funny calling this series the "marceloverse"; a marceloverse, in any case, should probably have more tea and comics and less twisted manipulation and bizarre scheming.) (Not that it'll stop me for writing more crack *g*)
They probably hadn't seen it yet. Perhaps couldn't see it, Shiva the heir of a timeless tradition of perfect warriors, Slade the too-perfect peak of a much shorter, but equally successful, government project. Both had worked as mercenaries, but neither of them had started like that. Neither had approached it as a business; it was big game hunting for Slade, and an artistic endeavor for Shiva.
They didn't really understand the concept of an investment.
They thought Cassandra was a failure, a pawn to be used against him. Shiva using her own temporary death to separate their daughter from the Bat had been, by all accounts, a beautiful maneuver. He didn't doubt that Slade had also had a hand, somehow, in Cassandra's rise to the head of the League of Assassins. At least he must have thought it funny.
Cassandra an assassin at last, but not under his control. Better yet, attacking another of his projects, a bait that might yet deprive the Batman of his current heir apparent, and himself of his control subject for the experiment. What could have been a worse failure for his training program?
They didn't understand that he had never expected Cassandra to grow into the perfect assassin - flawless physical ability was, in a way, incompatible with other necessary skills. A disappointment, they must have thought, too easily turned against him. Just like young Drake - although he had never suspected yet. None of them the perfect assassin that he had been looking for all those years.
Except -he reminded them in the privacy of his mind- that hooks trapped both fish and fisher; those two would fight and argue, but would never kill or stop the other.
They'd fall in love. Eventually, they'd have a child. He had made sure of that a long time ago, while he shaped their minds into the impressive tools they were.
A child with Cassandra's body and -he would arrange- training. A child with Drake's mind and early conditioning. A child inheriting the Wayne fortune and the Batman's resources.
Cain smiled in the darkness of his cell, waiting for Robin to come and "take him" to the oil field where the next stage of the drama was to take place. Pretty soon, as he and them accounted for time, he would have what he had been looking for these years.