If the bearings look good, as in no galling or overheating, they can be put back in. Are the lock tabs ok? They may have been flattened by installing them wrong, something to look at, they could be bent back.
I would remove the other main caps and be sure they are in right. Might take a look at the rod bearings, they may have not been oiling either. Make sure the rod caps are on right, the bearing lock tabs go both on the same side.
At least now you've found the problem, just hope nothing is damaged!