With what ARROW set up in S1 with being kinda grounded it is strange when meta human stuff happens and now supernatural things.
The Marvel Cinematic Universe did the same thing -- starting off with the relatively grounded
Iron Man before getting into more fanciful things like the Hulk and Thor and the Chitauri invasion. And then starting off on TV with
Agents of SHIELD, a spy procedural about normal, non-powered people, before phasing in more comics characters and superpowers. Heck, even their Netflix shows follow the pattern -- starting with
Daredevil, with his minimal superpowers that the show treated as little more than the practiced use of senses other than sight, then moving on to
Jessica Jones and
Luke Cage, which both have superpowered leads, and finally (if the original plan holds)
Iron Fist, which gets heavily into the supernatural/mystical stuff that was only vaguely hinted at in DD. The idea is to ease the general audience into the universe rather than springing the crazier stuff on them right off the bat.
The Arrowverse has been systematically adding more weirdness each year -- first unpowered vigilantes and villains, then the Mirakuru supersoldiers, then the accelerator explosion and metahumans, then time travel, and now magic in
Arrow and
Vixen and the multiverse in
The Flash. And coming up we've got miniaturization (The Atom), reincarnation (Hawkgirl)... it's pretty much no holds barred at this point.