As far as I can tell, the answer is as DoubleAA suggested in the comments: we don't really know why this is, and don't have enough data to find out. Mordechai Breuer, in his טעמי המקרא, discusses these verses (page 106). He points out three verses with a ma'ayla (מאיילא, which is what the servus is on the same word as the etnaḥta) preceded by another servus: these two, and Jer 2:31, which has אִ֛ם אֶ֥רֶץ מַאְפֵּ֖לְיָ֑ה (t'vir mercha ma'ayla etnachta).
He writes that the ma'ayla probably had a similar sound to a tip'ḥa, since none of the four verses that could contain the expected tip'ḥa before the etnaḥta are missing it (these three and Num 28:26), and the final melech is instead a zaqef qaton. He thus explains Jer 2:31: namely, t'vir mercha is a usual sequence leading into tip'ḥa, so the sequence makes musical sense. However, for the two Daniel verses, he writes that it is beyond us to give an explanation ("אין בידינו להסביר את ההטעמה הזאת").
Another explanation is proposed by Yochanan Breuer in his article מחלוקת ניקוד וטעמים בחלוקת פסוקים (again, thanks to DoubleAA for the link). In short (see page 38ff), he proposes that the accentuators have treated מאפליה as two words (מאפל יה), and although the written text has one word, the te'amim represent the intended te'amim for the two-word version, which is tip'ḥa etnaḥta. He then suggests that later ba'alei masorah reinterpreted this as a ma'ayla (and listed it in the Masorah Gedolah — see עין המסורה on בשבעתיכם). Breuer lists several similar words (שלהבתיה, כסיה/כס יה, ידידיה, הללו־יה, במרחב יה), and notes that in all cases, the te'amim treat them as two words (even though there is some disagreement regarding writing and niqqud); the same can be said for מאפליה. This gives an explanation for Jer 2:31 (whether it's a ma'ayla or a tip'ḥa is irrelevant to us). Thus, with only the Daniel verses containing an unexplained servus preceding a ma'ayla, we might conclude that the qadma in the Daniel verses preceding the is the usual servus preceding ma'ayla. However, with so few examples, any conclusion is only tentative.
Regarding the question of Rabbinic commentary on these verses: I have not seen anything mention the qadma preceding the ma'ayla.