Virtually all HVDC transmission currently operating is point to point mostly for control reasons. My understanding is it's very difficult to coordinate multiple converter stations - power flow in DC networks is fully determined by the control systems of the converters unlike AC networks which in general lack active control devices (see the FACTS family of devices for examples that can be used in AC networks to actively control power flow).

Not an expert but every node in an UHVDC network would need expensive equipment

Point to point is just two nodes, but scaling that outward would be very expensive

AC transmission is relatively cheap in comparison

Huge installed base of network elements, minimal efficiency improvements. Much better to invest in switch mode frequency stabilisation with batteries and soft open points (SOPs), which balance load between phases and distributors without needing a radial reconfiguration.

Radial DC is anachronistic thinking based on misunderstandings perpetuated by C-suite level just so stories like this Bloomberg nonsense.