Except Electric immunity is incredible for it, compared to immunity to a type it already resisted, for Chandelure.
Whereas Chandelure is 2HKOed by pretty much every offensive Electric-type out there and does not get anything particularly relevant from turning its Fire-type resistance into an immunity, Marowak flat-out stops almost all Electric-types thanks to many lacking coverage that is super-effective to one of Marowak's types.
This, alongside its other nine resistances that Chandelure could take advantage of if it weren't outclassed defensively.
Given how threatening Electric-types seem to be right now... Marowak is in a much better home than Chandelure.
Also, Marowak hits much harder without significant investment thanks to the Thick Club, which lets it get some bulk. Neutral-natured Marowak with 72 Attack EVs (or uninvested Adamant) has a higher offensive stat than a Modest Chandelure with maximum Special Attack EVs, with stronger STABs and a stronger coverage move in Bonemerang to boot.
How many top electric mons need to be stopped? Tapu Koko, Xurkitree..? So... that's all? Volt Switch I guess (in that case there are other options too)?
Dugtrio alone covers all your offensive electric type needs, while actually killing them for good.
Chandelure has Fire Blast (120), Overheat (130), Shadow Ball (80) and Hex (65/110) so Flare Blitz (120)/Shadow Bone(85) isn't "stronger STABS", at most the ghost stab hits 5 BP harder.
Ground type is good coverage... against the dreaded electric type only (steels won't come in, rocks have a lot of problems anyway, fire types won't come in because of your resistance to fire)? Ghost doesn't need much coverage anyway. Fire/Ghost is already fine with few resists.
Chandelure can threat water, ground and rock types with Energy Ball. That's 3/5, 4/5 with Ghost in terms of weaknesses covered.
Yes A-Marowak has stronger uninvested attack... with the cost of the item slot. Also A-Marowak kills itself with Flare Blitz which is bad for a pokémon which is supposed to be a check for things.
Chandelure has Trick to blast things off and to screw setupers/stallers. Also Sub+CM is a classic Chandelure set. That's good offensively and defensively. Or Leftovers if you want to go pure defensive, and you also can have Pain Split. Uninvested base 145 SpA STAB Fire Blast hurts enough for a defensive pokémon.
Speed is also important, you can burn T.Tar before it Pursuits you, you can sub before status.
So half empty half full glass.
TL;DR: A-Marowak and Chandelure are different pokémon that do different things.
As I said before A-Marowak is a GOOD pokémon and I'm not saying Chandelure is better, and definitively I'm not saying Chandy is better in the current Metagame.
I'm just surprised by the attention A-Marowak is getting as if it's suddenly revolutionary. I guess it's the Tapu Koko hype.