Alexander was not yet privy to the schism caused by his manipulation yet.
He also did not yet know just who Barzan really was, other than the fact that he seemed very loyal to Ptolomy.
And Alexander will only find out in the future that if the old man hadn't made himself a target at such an opportune moment that Alexander boldly capitalized on, it would have been very hard to kill the man later.
But fortunes favored the brave, and although he hadn't realized it yet, he had removed a major obstacle to making Ptolomy into a puppet.
At the moment, Alexander was blank to such consequences, and instead was looking at the dark skyline from his balcony on the third floor, as he had finished for the day.
After ordering the servants and a part of the soldiers to bed, organizing patrol routes for guards, taking a bath, and finishing his supper, he could finally relax, soaking in the monumental day he had.