Final answer:
The widespread belief in the Loch Ness Monster is likely due to cultural fascination and confirmation bias, despite lack of scientific evidence.
Step-by-step explanation:
The most likely explanation for the wide belief in the theory of the Loch Ness Monster, or ‘Nessie’, is not due to an abundance of evidence or difficulty in disproving claims, but rather a combination of folklore, wishful thinking, and psychological phenomena wherein people see what they want to see. Despite scientific surveys and advances in technology that have not substantiated the existence of such a creature, the theory persists. This can be attributed to cultural fascination with mysteries, the allure of the unknown, and confirmation bias, where individuals interpret ambiguous sightings in a way that supports their pre-existing beliefs about the monster.