Why hasn't this been done before?
This has been done before. Then why did the previous players fail?
1.1 They did not fail. So, competitors are out there. How are you differentiated? How will you take on their moats? How will you build your moat? If moats are shallow, can you really out-execute experienced players to win? How will they respond to your market entry?
1.2 They failed. What caused their failure? What is different now? How does that difference apply/accrue specifically to you, so that there are not a bunch of others also trying the same thing right now? How can you out-execute/out-compete all of these new players? HINT; "We're first to market" is not good enough.
This has not been done before.
2.1 Was the barrier technology? What has changed? It may be that you have a true innovation, which is great if you can protect and monetize it. (The latter is often easier said than done, as you need a whole ecosystem of partners, all of whom get a cut.) But true innovations are rare - new technology applied to an old problem is often simply better/faster/cheaper and not different in the sense of value delivered.* Then the question is better/faster/cheaper enough to break through the previous failure.
2.2 Was the barrier the market? What has changed? It may be that the market was just not ready and/or had too much inertia to be disrupted. Current players in any market have a vested interest. Whether it's capital deployed, union contracts, the regulatory regime - the current market can fight very hard. (As an example, read up on containerization in the transport industry... and how long the longshoreman's union slowed its introduction.) Being the disruptor is great; being the disrupted is not, and people will do much to avoid it.
2.3 Was the barrier the business case? Technology can do a lot of things, but the economics work for only a subset of those. Can you deliver the value for less than the price customers will pay?† Hint: you really should be testing pricing early with customers, before you build a great tech solution no one will buy at the price you need to charge.