The narrator says nothing negative about Othniel, and that appears intentional. The characterization of Othniel is unique among the deliverer accounts in that his is the only portrayal that lacks negative aspects. Nothing is said in this account that could be construed as negatively characterizing Othniel's motives or devotion to YHWH. Without exception, all the subsequent (non-Judahite) deliverers will evince some flaw of character that is paralleled, on an escalated level, by the negative portrayal of the deliverer's tribe or nation.
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7 And the people of Israel did what was evil in the sight of the LORD. They forgot the LORD their God and served the Baals and the Asheroth.