I agree. Far from a being a mere footnote, I am tending to accept the suggestion that the entire “Deuteronomistic History” (Josh-Judges -Sam& Kings -looking back on Deuteronomy) was compiled as a sustained argument/explanation as to why the chosen covenant people ended up in Babylon.
One effect of the Exile that my old bible school prof noted was that before the Exile idolatry in Israel was an on going and recurring problem. The exile seems to be the medicine that cured that particular sickness in the covenant people.
But I am not sure why/how you think it made “Judaism not ready for Messiah” Can you clarify a bit more?
Messianic expectation in Jesus time (400 years later) was still a powerful hope. Many of the prophets had seemed to say that the return from exile would culminate in the restoration of the Kingdom of Israel by the anointed “Son of David”. Ever since the return under Cyrus the government had not been a fully restored ongoing messianic kingship.
If anything the Exile seems to be the very thing that made a promised messiah a necessity.
Of course as is often typical, those in positions of power such as Herod and perhaps the Sadducees didn’t really want to relinquish power to any up-start messiah who might try to capture the public imagination based on the old prophesies.
Jesus wasn’t the only messianic candidate, and it seems his own disciples expected his ministry would include a resolution of the problem of those remaining in the exile lands (John 7:35)
After his resurrection one of their primary concerns / questions was whether his role as vindicated Messiah would most likely lead to the full restoration of the kingdom to Israel (Acts 1:6). Even after his ascension Jesus apostles considered it their responsibility to minister to the remnants still in the lands of the Exile (1Peter 1:1 James 1:1)