The strings of fate of the life forms in the known universe exist in a special dimension which only Saints can access and manipulate.
Primals were able to impact them, but manipulating them was completely out of reach. Only Saints could do that.
A person's life travels inexorably down his/her string of fate. Wherever that string of fate goes, so does that person. Whatever that string of fate goes through, so will that person.
The power of Saints over fate was no laughing matter.
Their power wasn't to merely subtly or indirectly influence what would happen to their targets in the future.
What they did was to create an immediate environment around the strings of fate which would directly impact the lives of their targets.
If a Saint wanted to bless a person, he would simply create a nurturing environment in the person's immediate future, and somehow, positive things would occur.