he had no absolute power
albatross was traumatized (+ sapphire) by the Event the occurred when he was just a child. lagoon repeatedly guilt-tripped him to get what she wanted, holding the event over his head. never let him live it down, never allowed him to heal. constantly reminded him of the mistake he made as a child. if you look in the book, the way lagoon and albatross are described are total opposites: albatross is described as "splashing in the waves" when with fathom, and lagoon is described as stalking out of the water. its clear that lagoon isnt a good dragon, especially with how she treats indigo (commoner's child). lagoon guilt-tripped, manipulated, and gaslit albatross to no end. she made it very clear to all that all albatross was was a toy for her, and that she would replace him the moment the summer palace was done.
albatross had no power in this. he was utterly helpless until he decided to go out with a bang (at the point of the massacre, he knew he was being replaced). even before then, anywhere you look in DS:L, every dragon has a relatively positive opinion of albatross. he's well-liked and lagoon is just a snob.
lagoon is the reason for the massacre, and its likely that albatross had a great jealous factor when regarding fathom. its just as likely that he wanted to save fathom from the tortures of being animus
regardless . go reread darkstalker: legends. tui makes it Very clear that albatross wasnt just ""insane all along,"" but that lagoon is Absolutely the one to blame