Wonder if the students simply accepted or is a brainwashing scenario and didn't even realize.
When I'm sure many kids would rejoice at becoming heroes instead of normal citizens everyone doing so would be difficult to believe.
I presume that the kids got blessed when getting isekaied and their easy to level and learn skill things is part of it, and people of that world have it harder, hence the summoning.
Only can think that the returners will likely become enemies of MC, their reward is keeping the power, and the goddess will not have a care about what they do with it.
Is even clear they will be stronger than MC for getting a actual training in using the power + enemies that help levelling up.