Caesar Petrovsky did not let Yuri feel victorious. Caesar didn't ask any further and just laughed. To him, Yuri was just a young man who happened to be friends with dangerous people. Now he was completely under the control of Avalon. Of course Caesar didn't have to do anything. He was not in a hurry. Even Though he was interested become like the Prince. Awakening his demon DNA would certainly make him stronger.
Like when he last faced his rival Raphael Chastain. When Raphael transformed, Caesar was shaken and maybe he could have lost then. Since then he has become more obsessed with demon DNA and hopes to awaken it too. But he wouldn't let Yuri take advantage of him. Caesar just needed to pass on what he just heard to Rutherford. Maybe the mad scientist could figure it out.
As far as he knew, the awakening of the demon DNA happened randomly. There was only one connection between all these cases, which was that they were all pure-blood vampires.
