It seemed historical enough; otherwise, why would the Jews create a holiday after something that never happened. One other holiday that the Jews created was Hanakah when the Jewish rebels held out against their enemies for eight days.
According to that, their candle holdier holding eight candles did not fully extinguish until the eight days giving them much needed light. It is questionable whether it actually happened, but if it wasn't true then the creators of that story would have made it far more sensational than it was.
I think similiarly, Esther could have also been embellished if it were not true. It was far yet the time when women can vote, but Esther saved her people with a very brave act at the very risk of her life, and she succeeded.
As for the absence of God's name that is troubling but it was among the last inspired books to be written before the five centuries of silence from the 5th cen. BC to the 1st cen. AD. Not only that, when it was written it was not that far from the actual historical figure as Xerxes who was born in rh 5th cen. BC as well.
Skeptics often criticised the New Testament gospels because they were written 30-60 years after the crucificion of Christ; but in comparison to other historcal records, it is far more credible as some, like the Illiad, were written 300-500 years after the event.
Back to the name of God, the original OT texts may contain the unobriviated name of God, but the oldest found OT text among the Dead Sea Scrolls, dated 100 BC) only have the tetragammaton YHWH (our Bibles uses LORD as you know).
To me, if true (that the original OT text contained the full name of God), this suggests that Esther was the very last inspired text to be written, then the scholars and scribes decided to no longer write His name there, and later decided to substitute His name and abbriviate it.
