I don't think it's at all surprising that there is no relation between tech stack and business success. End-users don't care if you use a single PHP file or a Go binary, they never get to see that anyway. So I don't really see "it was all a single PHP file" as a gotcha. The whole thing could've been coded in Assembly, the difference is in the effort required for development, ease of maintenance/scaling up and how well-guarded you are against vulnerabilities.