Aini's plan had Saleen feeling at ease with what would unfold in later days. He built his nation in haste, and it was kept together with the power provided by his backings. Without Jason's help, none of the nobles would have followed him.
The nobles would have fought in the future for more power and wealth, they even would have even toyed with the idea of independence. What Aini proposed allowed all that to be stemmed early.
Such sacrificial way of going about it was made possible due to the immense faith Aini had for Saleen and himself. From Aini's perspective, advancing to a become grade-10 death mage was only a matter of time, and he would live a long life when the deed was done. All the other dukes and duchesses would probably die early deaths, and he would have in time, become the most powerful duke in the empire. With that, he needed not fear anyone having opinions about him.