Most delays in software projects are not caused by hard engineering. They are caused by messages passing through too many people: a client talks to sales, sales talks to a project manager, the project manager talks to a lead, and the lead finally talks to a developer.
A small, focused team removes those layers. The people who scope the work are the people who build it, so there is no translation loss and no one to blame when something is unclear. Decisions that would take a week of meetings take a single conversation.
A small team also improves continuity. One builder can lead design and frontend while another owns the backend and deployment, and both stay close to the product decisions that shape the final result.
The trade-off is capacity: a very large programme with many parallel workstreams needs a bigger team. For websites, MVPs, e-commerce stores, dashboards and business apps, a focused team is often the faster and more affordable route.