In early islamic texts you will find making slavery easier again (the Eastern Roman Empire was phasing it out and tightening the rules significantly, because Christianity) was a goal of the early muslims, and you will find exactly why it was such an explicit goal, ie. what they wanted those slaves for ...

https://sunnah.com/muslim%3A1438a

https://sunnah.com/abudawud%3A2172

https://sunnah.com/bukhari%3A6603

So to answer your question: why bring back slavery? Free prostitutes, or even better: getting paid to rape random women you just abduct.

Ie. Why? Some things are just not available for free in any other system.

... and this is still being done today in some societies for that same "reason". So you can say it succeeded.

https://archive.ph/JYcJg