From the perspective of original Dungeons and Dragons, what is being called a "cleric" here is faulty by many people. Cleric here is taken as "healer" from the MMO triad of "tank, healer, DPS". That's gamey, and very specific.
In pre-OD&D, the Cleric was invented in the Arneson campaign in order to correct the problem that were vampires, especially vampire player character. Therefore his main feature was Turn Undead. This created a (very confusing) triad of fighting-man, magic-user and cleric, each taking different role. Because of his love of history, Gygax gave it a more "clerical" touch with influences of old school heroes that we now would call "paladin" or holy man, such as saints, templars, but also some figthing bishop of second of half of middle ages. This stired the class in two different but complementary direction: a mace-wielding holy man from the middle age, and a Van Helsing figure from the Hammer film (horror movies).
That being said, both those influence were very specific: Arneson Van Helsing, and Gygax middle-age bayeux tapestry figthing bishop. When the game (d)evolved, the class lost this christian touch and anti-vampire/monster touch. This created a hole in its reason to exist. So instead of getting rid of it, it was repurposed.
Personally, I think that in most cases, the cleric shouldn't exist, or should be really thought of more thoroughly.