The three Sovereigns were many times stronger than Vico and Callie.
As much as these two were at level 100, their cultivation base was so weak that they couldn't even be considered Divine Journey cultivators. Only when their powers developed, their foundation improved, could they be considered Sovereigns, or Divine Journey cultivators.
They had difficulties that the Sovereigns in the group didn't have.
As their conversation showed, while it would take Vico and Callie at least a century to create a good, stable Spatial Kingdom big enough to become a headquarters, the three Sovereigns had made places as big as the Ancient Dragon Spatial Kingdom in just weeks of hard work.
In fact, the strongest of them, the level 103 Sovereign, had created two Spatial Kingdoms during his 12 months in the Spiritual World. He made one for his old family and another as an inheritance, where his future heirs and geniuses of the world could compete for growth opportunities.