The 2.5 tribes claimed (Num 32,4):
הָאָ֗רֶץ אֲשֶׁ֨ר הִכָּ֤ה ה' לִפְנֵי֙ עֲדַ֣ת יִשְׂרָאֵ֔ל אֶ֥רֶץ מִקְנֶ֖ה הִ֑וא וְלַֽעֲבָדֶ֖יךָ מִקְנֶֽה׃
the land that the LORD has conquered for the community of Israel is cattle country, and your servants have livestock.
G-d promised the people the land of milk and honey (Exodus 3,8 and more)- the milk of livestock, meaning inG-d's eyes/plan the land is specifically fit for it. The spies verified that claim (Num 13,27). And G-d was very angry when the spies claimed that the land is not fit (for many reasons).
However, the tribes openly suspected that the promised land is not fit for their needs, what seems to constitute slander.
Moses openly compares it to the slander of the Spies (ibid 16):
וְהִנֵּה קַמְתֶּם תַּחַת אֲבֹתֵיכֶם תַּרְבּוּת אֲנָשִׁים חַטָּאִים לִסְפּוֹת עוֹד עַל חֲרוֹן אַף־ה' אֶל־יִשְׂרָאֵל׃ כִּי תְשׁוּבֻן מֵאַחֲרָיו וְיָסַף עוֹד לְהַנִּיחוֹ בַּמִּדְבָּר וְשִׁחַתֶּם לְכָל־הָעָם הַזֶּה׃
And now you, a breed of sinful men, have replaced your fathers, to add still further to the LORD’s wrath against Israel.
If you turn away from Him and He abandons them once more in the wilderness, you will bring calamity upon all these people.”
However, Moses' critique seems only to address the fact of the conquest, not the settlement, which Moses agreed very quickly. But for me, the very fact of the settlement outside Israel seems like an act of distrust of G-d and His promise.
Why 2.5 tribes' claim wasn't considered slander against Eretz Israel and they weren't punished?