Literally: "But, surely, let it have been a preparation of a kindom/reign to give their things back to the people".
The construction with the perfect subjunctive, in this case, means that the author is conceding this argument, even if it may not be true.
In more usual English you could say something like: "But let us assume that giving their things back to the people indeed meant that he was preparing to become king."
The construction with the perfect subjunctive, in this case, means that the author is conceding this argument, even if it may not be true.
In more usual English you could say something like: "But let us assume that giving their things back to the people indeed meant that he was preparing to become king."