Assumption being the mother of all f-ups ... thinking dnsmasq gets started for its DNS caching capabilities.
Totally forgetting it can also do DHCP.
Notice the --dhcp-range= argument above.
Am pretty sure some NM setting you configured triggers dnsmasq getting started for its DHCP server capabilities (pihole-FTL can also take over this part).
Can you post output for below ?
sudo grep -v '^\s*#\|^\s*$' -R /etc/NetworkManager/ --include=*.conf | sort | sed 's\:\ \' | column -t
Dit you create some sort of NM profile for connection sharing or similar that depends on running your own DHCP ?
EDIT:
nmcli connection show --active
Replace <UUID> below with the one found from above:
nmcli connection show <UUID>
EDIT2: might want to redact some of the output for that last one !