Your debug log shows nginx also running on port 8080:
*** [ DIAGNOSING ]: Ports in use
*:1880 systemd (IPv6)
*:3000 systemd (IPv6)
*:8000 systemd (IPv6)
*:22 sshd (IPv4)
*:22 sshd (IPv6)
[80] is in use by nginx (https://docs.pi-hole.net/main/prerequisites/#ports)
[80] is in use by nginx (https://docs.pi-hole.net/main/prerequisites/#ports)
*:8080 nginx (IPv4)
*:8080 nginx (IPv6)
[80] is in use by nginx (https://docs.pi-hole.net/main/prerequisites/#ports)
[80] is in use by nginx (https://docs.pi-hole.net/main/prerequisites/#ports)
*:8080 nginx (IPv4)
*:8080 nginx (IPv6)