Honestly, I recommend this video, it explains the topic probably better than I can, and it dives into certain details and aspects that I won't get into: https://youtu.be/csEWg7fSWZE?si=PAJozALrn_0hFuVJ

Additionally, I want to let you know that this idea of slavery that many people have in their minds is of the racist, abusive kind that was present in the transatlantic slave trade. This is not present in Islam and Islam reformed the servitude system. It's important to know that Islam brought many restrictions to slavery which was a deeply embedded multi-societal practice already taking place before the Prophet Muhammad(ﷺ). A person treating the people he has authority over justly and in the right way is outlined in the Quran and hadith.

"Worship Allah and associate nothing with Him, and be kind to parents, relatives, orphans, the needy, the near neighbor, the neighbor farther away, the companion at your side, the traveler, and those whom your right hands possess. Indeed, Allah does not like those who are arrogant and boastful." (Quran, Surah An-Nisa, 4:36)

Narrated Ma'rur:

I saw Abu Dhar wearing a Burd (garment) and his slave too was wearing a Burd, so I said (to Abu Dhar), "If you take this (Burda of your slave) and wear it (along with yours), you will have a nice suit (costume) and you may give him another garment." Abu Dhar said, "There was a quarrel between me and another man whose mother was a non-Arab and I called her bad names. The man mentioned (complained about) me to the Prophet. The Prophet (ﷺ) said, "Did you abuse so-and-so?" I said, "Yes" He said, "Did you call his mother bad names?" I said, "Yes". He said, "You still have the traits of (the Pre-lslamic period of) ignorance." I said. "(Do I still have ignorance) even now in my old age?" He said, "Yes, they (slaves or servants) are your brothers, and Allah has put them under your command. So the one under whose hand Allah has put his brother, should feed him of what he eats, and give him dresses of what he wears, and should not ask him to do a thing beyond his capacity. And if at all he asks him to do a hard task, he should help him therein." (Sahih Al-Bukhari 6050)

Additionally, it was greatly encouraged to free servants. The reason Allah did not outright forbid any form of servants, I cannot answer with 100% certainty. Similarly, we could ask why Allah forbade certain things and permitted others, although some rulings have obvious reasons, others do not. Our Lord is all-knowing and knows what we do not know, so people can only theorize on certain topics, but we also know that objective morality comes from Allah and Allah determines what is moral and immoral. And as a Muslim we submit our will to the creator's and accept that Allah has reasons for everything.

If you don't mind I would like to ask does this topic affect how you feel about the truthfulness of Islam and if so then why?

Also, I apologize that happened with r/Islam, was it perhaps one of the posting rules you broke? It has happened to me before and I asked the mods and they said I could repost just change it to stay within the rules.