The blood God decided to compete with link in terms of numbers.
Then, link would just take out his Zerglings and pets to compete in numbers!
The souls in zul 'er's blood sea were the batch of zealots who had sacrificed themselves. There were no more.
therefore, despite zu xuan 'er's great fanfare, there were only so many souls in his hands. no matter how wide the blood sea was, the number of bloodsouls he could use was constant.
This was mainly because link didn't play by the rules. While they were planning, he released the signal from the evil God's skeleton.
The blood God and the God of plagues were afraid that link would contact the stellar Union. By then, both the blood God and the God of plagues would have to face a leap in the number and quality of enemies.