Are there any rabbinic sources that offer a hashkafic/spiritual explanation or explanations as to why he died? There aren't many Chazalic sources that reference the Maccabees, so I'm looking for anything from the Gaonic period and onwards (but if there is a Chazalic source out there that presents an answer, I'll be more than happy to see it).
Ramban Bereishis 49:10
וזה היה עונש החשמונאים, שמלכו בבית שני, כי היו חסידי עליון, ואלמלא הם נשתכחו התורה והמצות מישראל, ואף על פי כן נענשו עונש גדול, כי ארבעת בני חשמונאי הזקן החסידים המולכים זה אחר זה, עם כל גבורתם והצלחתם, נפלו ביד אויביהם בחרב, והגיע העונש בסוף למה שאמרו רז"ל (בבא בתרא ג.): "כל מאן דאמר מבית חשמונאי קאתינא עבדא הוא", שנכרתו כלם בעון הזה. ואף על פי שהיה בזרע שמעון עונש מן הצדוקים, אבל כל זרע מתתיה חשמונאי הצדיק לא עברו אלא בעבור זה שמלכו ולא היו מזרע יהודה ומבית דוד, והסירו השבט והמחוקק לגמרי, והיה עונשם מדה כנגד מדה, שהמשיל הקדוש ברוך הוא עליהם את עבדיהם והם הכריתום.
The rabbis did not approve that the Hasmonean dynasty, issued from the Maccabean revolt, assumed the kingship of Israel, instead of giving it back to David’s family. The Torah says the kingship belongs only to David’s family:
The staff shall not depart from Judah [David’s tribe], nor the scepter from between his feet, until Shiloh arrives, and to him shall the obedience of the people be. [Gen. 49:10]
The Ramban writes ties the death and disappearance of Hasmoneans to their taking the throne:
In my opinion, the kings who reigned over Israel who came from tribes other than Judah, after David, were violating the expressed wishes of their forefather Jacob and were usurping Judah’s rightful inheritance… And this was the punishment of the Hasmoneans who ruled as kings during the Second Temple [period]. [Now,] they were [certainly] righteous people, and if not for them, Torah and mitzvot would have been forgotten by the Jewish People. Even so, they were punished with great retribution: … All their descendants were killed off because of this sin. [Ramban on Gen. 49:10]
Not really an explanation per se, but Rabbi Hershel Schachter points out that it was treated halachically (at least in its earlier stages) as a milchemes reshus, not a milchemes mitzvah, because the odds were so seriously stacked against them. We couldn't demand people go on a suicide mission. (This explains the line from the historians about the mashuach milchama giving the "go-home" talk before the battle.) So the loss of a leader like that just proves the point.