This isn't about technology though. It's about resources. The London Times correctly identified that if the proliferation of horses were to continue, the streets would be covered by manure. The solution to this problem was to stop using horses, which is exactly what happened, although of course not everyone was able to see it at that time.

And that's precisely the point. People investigated alternative means of transportation while they still had the luxury of doing so. Not because of fear of manure, of course, but because they realized that horses were non-ideal in many other ways. Imagine what would have happened if the streets had been covered by nine feet of manure, and only then people started thinking about ways of getting out of that mess (literally).