Capital is just a motivator for people not otherwise invested in the project, really. These projects can be done without capital if enough people agree they're beneficial.

Now, people's skillsets differ so maybe a village's folks aren't enough to take on a project they desperately need - but even then, you don't need capital to persuade someone from another village to join in and help. You could exchange labor of a different skillset (you help me build X, I help you with Y), etc.

As for equipment - they dug it with shovels, literally. It's not a long street, roundabout 10 houses on either side. Engineering - no idea, but I'm assuming there was a project already, but nobody to do the physical work.

Cool example. I did think twice before saying a community can’t build a bridge or dam

You were right there - it depends. If a beaver can build a dam, so can a community. A community probably won't build the Hoover Dam, though - unless the community is hundreds of thousands of people (that can allocate several thousand to designing and building the thing). Same for bridges. In my country the leftover DIY mentality from the harder times in history is so strong, if you have a stream running through your property and you need a bridge over it, you build it yourself, or get your family or friends together to do it together. Usually that would mean pedestrian bridges of course. BUT I've also driven my car over wooden bridges that looked like they were built by the very small local community and felt very sturdy. That would be to go to the parking lot of a nature trail of course, not something on a public highway lol