I would like to add following things to the list
1 - Wrong timing of the Product:
Even though your product is excellent, sometimes business fails because market is not ready to buy or understand your product
2 - Poor Marketing:
Marketing is crucial for any business. If you do marketing at wrong section of people, your marketing fails and so your business.
And there is one other factor - which is the external factor
Like the product were released at good time and marketing too was good but COVID damaged everything. Sometime we can't do anything.. When the big businesses were falling mask making companies flourish like crazy. This is called. Luck