for mass/consumer market - the idea must be usable to me before I expect others to use it, making money is not easy thing due to long waiting time. recently hybrid platforms (digital + physical) got good success than purely digital one's. I think, passionately working on by 'watching' what customers do with the product is key to success. Usually people have passion in the idea stage, deciding based on hype is always leads to failure. mass market is a marathon race, luck plays critical role.

for enterprise - may be able to make money earlier than consumer market. I think reading "startup" books provides good insights, process to follow.

for niche: domain knowledge, few early customer are critical for success. may be able to reach customers easily, may not be able to scale.

Generally, speed and assumptions decide fate for any idea. particularly "assumptions" are the #1 enemy of every idea/startup.