Of course, we have no understandings about these giants. But we can suggest that Eliezer had such a strong Chinuch from Avraham Avinu to go against his Negi'a, that it wasn’t an issue at all! It was obvious that Eliezer wouldn’t get insulted, and he would gladly go against his own Retzonos to get Yitzchok a: בָּרוּךְ “blessed” (girl) and not his own “cursed’ daughter.
In our terms: Going against your Ratzon was the “in thing” in Avraham Avinu’s house. “That’s what we’re all about around here!” Especially since the Gr”a says: עִיקָר חִיּוּת הָאָדָם שְׁבִירַת הַמִּדוֹת, וְאִילּוּ לָמָּה לוֹ חַיִּים – What other purpose is there for a person to be alive, other than for him to work on going against his Middos! This may also explain why Eliezer wanted that Yitzchok's future wife should be extreme in Chesed, and say: וְגַם גְּמַלֶּיךָ אַשְׁקֶה – “Not only you can have a drink, but I will give your camels to drink as well”, since Avraham Avinu was extreme in Chesed (he ran as an old man, on a day of Sakana (medical risk); i.e., the third day after his Bris Mila, and: וְאֶל הַבָּקָר רָץ אַבְרָהָם – he ran to Shecht 3 cows, just for their tongues alone).
In a world of selfishness (especially in such a close proximity to Sedom, where Chesed was outlawed; punishable by death. Chazal) you need to go extreme in Chesed. (Rambam). Also, we see how Avraham Avinu wasn’t afraid to send an עֶבֶד (slave), notorious for being: שְׁתוּפֵי זִימָּה lacking in morality, to bring a young girl on a long trip. Avraham Avinu was pure, and his surroundings were pure.
