וַיֹּצֵא֩ מְנַחֵ֨ם אֶת־הַכֶּ֜סֶף עַל־יִשְׂרָאֵ֗ל עַ֚ל כָּל־גִּבּוֹרֵ֣י הַחַ֔יִל לָתֵת֙ לְמֶ֣לֶךְ אַשּׁ֔וּר חֲמִשִּׁ֧ים שְׁקָלִ֛ים כֶּ֖סֶף לְאִ֣ישׁ אֶחָ֑ד וַיָּ֙שָׁב֙ מֶ֣לֶךְ אַשּׁ֔וּר וְלֹא־עָ֥מַד שָׁ֖ם בָּאָֽרֶץ׃
Radak on II Kings
He did not stay there but returned to his home seeing that he recived the money and no longer protect him from other enemies