The collapse of ABC Learning was mainly due to the lack of corporate governance and internal control failures. The company made several major acquisitions without proper due diligence and valuation, leading to overvaluation. Similarly, other companies like Tel Phone and XYZ Inc. also suffered from similar issues, ultimately leading to liquidation. This highlights the importance of maintaining ethical practices and following accounting assumptions, such as going concern, to avoid financial crises. It is essential for auditors to be unbiased and not influenced by management or peers.