Pharisees and Sadducees

Is this an argument from providence?
Because if there is no providence then theoretically maybe the Sadducees are the true keepers of the word of God, and rabbinical law randomly took over Judaism. No?

Not related to supervision. There are evolutionary processes in halacha, and thus the halacha that is accepted has a binding status. Certainly where you do not have a clear position, there is another system/opinion that is correct.
To the same extent, I do not know how to decide that Rabbi Yehuda is wrong, and yet they rule as if he did not intend and as if he did not intend and so on. Or as a rabbi against Abaye except for Yael KJM.

Why do you assume that accepted law has binding status,
This is itself a Pharisaic assumption. The assumption of the Judean Desert sects would speak of their correct law. Not religious evolution and that is why they withdrew to the desert.

Everyone claims to be right. So what? Logic says that there is validity to public acceptance, just like the covenant we made at Mount Sinai. I suppose the sects also admit that the system they accepted is binding on them.

As for dynamic tradition, see the latest Toray series (622 onwards).