It sounds like you failed for many reasons, lean being the least of them. "Lean Startup" doesn't mean you should wait to raise, it means that you can get more "at bats" with the money you do have. Just because "lean" made it possible to not raising more money right away, that doesn't mean it's part of lean - that was a bad idea by the founder. And think about it this way, let's say you decided to "go big" and not raise right away - how much faster would you have gone bankrupt? The issue here is the lack of fundraising, not lean.
It feels like you took a bootstrapper approach to building your company, but within a YC incubator talking to VC investors.
No matter what methodology you use, that team sounds very small. I really hope the "1 founder" was a developer and an amazing design was crucial for your companies success.... :)