Final answer:
The religious fanatic serial killer who killed landladies all over the US and Canada in the 1920s was Earle Leonard Nelson, also known as 'The Gorilla Man'. He targeted elderly landladies, gaining their trust before strangling them to death. Nelson's hulking appearance and gorilla-like grunting during his murders earned him his nickname.
Step-by-step explanation:
The religious fanatic serial killer who killed landladies all over the US and Canada in the 1920s and was given the nickname 'The Gorilla Man' by the press was Earle Leonard Nelson. Nelson was an American serial killer who embarked on a killing spree between 1926 and 1927. He targeted elderly landladies, and his modus operandi involved gaining their trust and then strangling them to death.
Throughout his crime spree, Nelson traveled extensively across North America, committing murders in multiple states and even Canada. He preyed upon vulnerable women, taking advantage of their hospitality before taking their lives.
Nelson's actions and the terror he caused earned him the nickname 'The Gorilla Man' due to his hulking appearance and the gorilla-like grunting noises he made during his murders. He was eventually captured, convicted, and executed in 1928.