I think Torah says it pretty much explicitly (Ex 18.3):
וַיְהִי מִמָּחֳרָת וַיֵּשֶׁב מֹשֶׁה לִשְׁפֹּט אֶת־הָעָם וַיַּעֲמֹד הָעָם עַל־מֹשֶׁה מִן־הַבֹּקֶר עַד־הָעָרֶב׃
... כִּי־יִהְיֶה לָהֶם דָּבָר בָּא אֵלַי וְשָׁפַטְתִּי בֵּין אִישׁ וּבֵין רֵעֵהוּ וְהוֹדַעְתִּי אֶת־חֻקֵּי הָאֱלֹהִים וְאֶת־תּוֹרֹתָיו׃
Next day, Moses sat as magistrate among the people, while the people stood about Moses from morning until evening. ... When they have a dispute, it comes before me, and I decide between one person and another, and I make known the laws and teachings of God.”
They were LITIGATING. Think yourself, they had lots of property, livestock, slaves, and they were terribly bored, as you mentioned - no need to hunt, grow crops, cook, wash dishes, not even using the bathroom (חוץ מכבודכם), etc. So they were suing one another just about everything - "this is my slave... this is my piece of Manna... my bull, etc".
They were so "obsessed" with suing each other they needed a total of 78.000 judges (Yitroh's advice Sanh 18) for 600.000 males (let's estimate the whole population to be 6 fold of that - 3.6M), or 2.200 judges per 100.000, while in the USA it's less than 2 judges per 100.000.
I'm probably wildly exaggerating, they had some spare time to argue with Moses, prepare sacrifices, do some politics (Nesiim, Zkenim, etc), sin with gentiles, and, of course, learn Torah with Moses (where available).