The Sassanid Empire had various Cataphracts and horse archers which were much more powerful than the naked Visigothic warriors,but the Sassanids not only couldn't sack the City of Rome throughout its history but they even got their capital besieged by Julian in 363.In contrast the Visigoths annihilated the Roman army led by Valens in 378 and sacked the City of Rome in 410.Why couldn't the Sassanian army crash the Romans in Roman soil and sack the City of Rome prior to the Goths?
Hey there,
Just to let you know, your question is fine, and we're letting it stand. However, you should be aware that questions framed as 'Why didn't X do Y' relatively often don't get an answer that meets our standards (in our experience as moderators). There are a few reasons for this. Firstly, it often can be difficult to prove the counterfactual: historians know much more about what happened than what might have happened. Secondly, 'why didn't X do Y' questions are sometimes phrased in an ahistorical way. It's worth remembering that people in the past couldn't see into the future, and they generally didn't have all the information we now have about their situations; things that look obvious now didn't necessarily look that way at the time.
If you end up not getting a response after a day or two, consider asking a new question focusing instead on why what happened did happen (rather than why what didn't happen didn't happen) - this kind of question is more likely to get a response in our experience. Hope this helps!