1)
What is the meaning of "va'Yashar"?
1.
Radak, Malbim: It is from a two-letter root, like Sherarah (authority). Because he ruled by himself, and not over (for the sake of) all of Yisrael, it says va'Yashar, and not va'Yishpot. He did not go in a good path or return Yisrael to repent.
2)
Why does it say "va'Yashar", and not va'Yishpot?
1.
Radak: He ruled by himself, and not over (for the sake of) all of Yisrael. He did not go in a good path or return Yisrael to repent.
2.
Malbim: He did not judge. He merely ruled by force.
