Because of conveying the great mountain for a long distance, King Indra, Mahārāja Bali and the other demigods and demons became fatigued. Being unable to carry the mountain, they left it on the way.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
दूरभारोद्वहश्रान्ताः शक्रवैरोचनादयः । अपारयन्तस्तं वोढुं विवशा विजहुः पथि
dūrabhārodvahaśrāntāḥ śakravairocanādayaḥ | apārayantastaṃ voḍhuṃ vivaśā vijahuḥ pathi
SB 8.6.34