This team is basically built around Mega Gengar making the game awkward for the opponent.
Gengar traps things in, so once the opponent has a bad Pokémon on the field, they can’t just switch out for free. That makes Whimsicott, Raichu, Arcanine, and Dragonite way more annoying to deal with.
The main plan is to use Whimsicott for Tailwind or Raichu for Fake Out, then let Gengar start applying pressure. While the opponent is stuck, you can slow them down with Nuzzle, burn physical attackers with Arcanine or Gengar, or clean things up with Dragonite.
Swampert gives the team a solid bulky attacker that helps into Fire, Rock, Steel, and Electric types, while Arcanine keeps the team safer with Intimidate, Snarl, and Will-O-Wisp.
So overall, it’s not trying to win with one big setup. It wins by controlling the board, trapping bad positions, and slowly making the opponent run out of good options.