A few thoughts.
(1) You don't need 71 blocklists and 3.9 million domains on blocklist to block ads. Lack of blocklists is not the reason you were seeing ads.
Note that this entry appears to have combined two URL's into one line (problem):
https://v.firebog.net/hosts/Easylist.txthttps://pgl.yoyo.org/adservers/serverlist.php?hostformat=hos
Why were/are you seeing ads? Your Pi-hole is working properly per your debug log, so it's one of these reasons.
(1) Client(s) are not using Pi-hole for DNS. Do you have any other DNS resolvers available to clients, other than Pi-hole? Any "secondary" DNS servers in the router?
From a client that you believe should be connected to the Pi-Hole for DNS, from the command prompt or terminal on that client (and not via ssh or Putty to the Pi), what is the output of
nslookup pi.hole
(2) Even if the client is using Pi-hole for DNS, if you are using a browser with private or secure DNS settings, DNS traffic will go somewhere other than Pi-hole.
(3) If you are using a VPN service on a client, DNS traffic will bypass Pi-hole.
(4) Some ads cannot be blocked by Pi-hole. YouTube, Facebook are two examples.