Not true. It was rich, yes. The emperors took it all. The common people got nothing. Hence the big tombs etc. Indigenous institutions were destroyed, libraries and universities burnt. Religious structires destroyed and natives under constant threat and conflict. This is directly reflected by the complete lack of pioneering work in science, technology, astronomy, mathematics, philosophy and literature during this period. All of that was pre islamic invasion.

Yes prosperous. Minus the brutal and barbaric genocide, oppressions, etc. Obviously such colonialism destroys culture and wealth even if a few powerful outsiders extract wealth for themselves. You’re whitewashing Islamic colonialism for some weird reason.