Krishna had detected that the king of heaven, god of rain, Indra was overcome with pride of his exalted position. Krishna wanted to cut down his conceit and teach humanity a valuable lesson in the process.
When the denizens of Vrindavan under the stewardship of Maharaja Nanda prepared to perform their annual sacrifice to Indra for obtaining sufficient rainfall for their agriculture, Krishna deliberately undermined Indra’s position before the Vrajavasis and induced them to perform a grand puja for Govardhana hill instead.
Infuriated, Indra showered catastrophic rainfall on Vrindavan and in the midst of the devastation, the inhabitants of Vrindavan helplessly called out to Krishna. Krishna told His beloved devotees to not be disturbed. He then lifted Govardhana hill on the little finger of His left hand and held it up like an umbrella for the cowherd families and their herds to take shelter. As a child lifts a mushroom effortlessly, Krishna held up Govardhana hill for 7 days and 7 nights. The Vrajavasis felt no hunger, thirst of fatigue under the Govardhana and spent the whole time in jubilant singing and dancing. Indra realized Krishna’s supreme position and humbled, offered remorseful prayers to Him.
Even though Krishna mentions in the Gita that He has established a system of reciprocation between humans and demigods (BG 3.11), He also teaches that for a person fully surrendered to Him, He ensures his worldly sustenance (BG 9.22). Those deluded by material desires worship the demigods for selfish gains (BG 7.20). The Govardhana pastime is a lesson to human society to take complete shelter of Krishna and fully depend on Him. No power of the universe can harm such a society.