In HoloWorld there is no central authority that can decide to spend everybody else's resources based on their own narrow agendas. Large projects are only made possible by large numbers of people voluntarily donating their support and their resources to their accomplishment.
A large project comes together by resonance. An idea is brought forward, by an individual or by a small team, and communicated to others. If others find the idea attractive it is disseminated widely and rapidly.
People will essentially vote a large project into existence. They will vote by directing their attention, their financial resources, and their manpower to the project. This is in part possible because those resources are free; they largely aren't bound into fixed structures that are controlled by others. Most HoloWorlders have free resources that they can direct at their discretion towards common goals.
Large construction projects are not financed by loans. They are created from donated resources. They are not designed behind closed doors, the proposed designs are scrutinized by thousands or millions of people, because those are the people who will decide or not to commit their resources to them. Proposed projects that aren't being made public or that don't find resonance with many people will simply not happen.
Naturally, the projects that will find approval from the most people will be the ones that benefit the most people, projects that distribute their benefits widely and that aren't vulnerable to central points of control.
This likely means large energy producing devices, such as orbiting solar gathering satellites, dams, or tidal generators. It probably means large collective living structures, such as arcologies, space stations, and ocean bottom cities. It might also mean surprising constructions that would never be financed in traditional ways, such as multi-square mile paintings, shrines to popular celebrities, enormous entertainment or sports installations.