Actually it reinforces that the idea actually is the easiest part of the equation. Execution is the key and the winners are the ones who executed the best. You can't compare Webvan to Amazon.
Amazon ended up owning and operating Webvan.com.[1] The people who developed Webvan went on to develop Amazon Fresh.[2] The founder of Kiva Robotics, which was acquired by Amazon, was from Webvan. Amazon's grocery business is directly descended from Webvan.
[1] https://web.archive.org/web/20160303194049/http://www.webvan...
[2] https://www.reuters.com/article/net-us-amazon-webvan-idUSBRE...