How did Pokemon letsgo Gengar get it?

Gengar can only evolve into Haunter through Gastly, and then players need to communicate with players to evolve into Gengar, while Gastly can be captured in the Baokemeng Tower in Resource Town.

Gengar's new player has only one elf, which makes him the king of popularity. The reason why so many players can't do without its super attack power and field control ability is because they have good explosive ability, no matter which elf they play against.