My Uncle is a holocaust survivor and asked me why Jews didn't return to Israel after the fall of Rome since they were persecuted. I didn't have a great answer, but I guessed it was because Jews had made their lives elsewhere and the Byzantine empire still controlled the area until the latter half of the 600s. After that I had no idea because Islamic Caliphates tolerated Jews like Maimonides. I suppose Jews who had lived elsewhere for generations never felt a pressing need to ever return. Travel was probably relatively expensive and dangerous, but I feel like I'm missing something.
Delayed response here but I'll have a go at an answer. You pretty much got all the major reasons why Jews didn't return back to Israel after the fall of Rome
They were settled where they lived by that point and didn't want to uproot their lives
The journey there would be dangerous and very expensive
Jews were sometimes forbidden to travel to Israel by the local governments
Jewish communities are very strong and an essential part of the culture. It is important to live near other Jews for religious customs and so if they didn't know what the community would be like in Israel, many Jews would rather just stay where they were
At that point, Israel was viewed as a theoretical place, not somewhere easy to travel to and go. Jews have ALWAYS prayed for and talked about returning to their ancient homeland but this was just a pipedream until 1948 for most.
Yes they were being persecuted where they were living, but who is to say they wouldn't be persecuted in Israel also? Better to stay in the hardships you know than travel to the unknown