I am 99% sure what is happening is casual invades appear on defenders as wins for 1 point. Easy 1 trophy, meh gold, but you probably have 1 troop defence, meaning it's super fast. Also, only 50 gold to refresh for a new opponent.
The devs have not responded about this "feature".
But it's Technically legit ^^ Also had other people invade multiple times in a row.