> The only one I don't understand is how NDP is simpler than ARP. ARP is an Ethernet broadcast while NDP is built on IPv6 multicast

ARP is a special protocol implemented on the data link layer, while NDP is just another type of ICMPv6 packet.

> which creates a recursive chicken and egg situation

I believe that NDP mostly uses the special ff02::/16 link-local multicast addresses [0], which don't require any configuration to use.

[0]: https://www.iana.org/assignments/ipv6-multicast-addresses/ip...