Can 10000 troops beat 101 in real life? I think yes. There needs to a "brute force" rule in the attack calculations. Something like x to 1 troops will defeat all remaining troops in a castle (or attacking a castle).
X could be anything reasonable like 250 or less to one. If I send 25,250 troops to a castle, it should be able to easily defeat 101 troops in a round. Same thing with defending. That many defenders should be able to easily kill 101 attackers.
100 to 1 sounds better but I am just throwing numbers out there.
I actually quit US1 for awhile just because I was tired of little players constantly attacking then defeating 50000 troops by trickling until all their alts jumped in to send defense.