There is a fundamental difference between Avraham and Yitzchak.
Avraham primary middah/ attribute was chesed- loving kindness. he was involved in actively try to fix up the world, including getting people to recognize G-d and try to live a G-dly life.
We constantly find Avraham involved with other people- setting up altars and "calling in the name of Hashem" (chap. 12-13), rescuing Lot (chap.14), greeting the angels and taking care of them (Genesis Chap. 18), praying for Sedom (ibid.), dealing with Avimelech (chap. 20) etc. He took a very active role in this world, trying to bring it to perfection.
Perfecting the world requires fixing up wrongdoings.
Yitzchak, on the other hand, exemplified the middah of Gevurah- power and self-restraint. He accepts whatever comes his way, recognizing that it is the will of Hashem.
Thus we find that at Akeidas Yitzchak- when Avraham binds Yitzchak and prepares to sacrifice him- the verse says that Elokim tested "Avraham"- not Yitzchak (22:1). For Avraham it was a test, since sacrificing his son went against his very essence of loving kindness.
But Yitzchak went along willingly (See Rashi's commentary on verse 6). We find no resistance on his part at all.
Likewise, in the story of the blessings (Chap. 27), Yitzchak takes a very passive role as Rivka arranges for Yaakov to take Esav's blessings.
This is because Yitzchak's role was to develop his relationship with Hashem and completely give himself up to His desires.
So when Avimelech's servants take his wells, Yitzchak doesn't fight back. He accepts it and moves away. His passivity is not because he is weak or unable to fight back. Rather he accepts that whatever happens to him is exactly what Hashem wants to happen, and thus he just accepts it willingly.
I have heard this idea in numerous forums from Rav Moshe Shapiro zatza"l and some of his talmidim, including specifically Rabbi Dovid Orlofsky. The basic concept- Avraham represents chesed and Yitzchak, gevurah- is very commonly discussed among the commentators like Maharal.
I do not know if he had a source which specifically discussed the application to the wells, or if that was his own insight.