That's hype for Enel's fruit.
I wouldn't really say that because Enel's fruit's specialty is literally lightning while Big Mom can spam several elements AND still showed similar feats to Enel's main assets which definitely ain't bad.
Since maxim was only there to generate thunder clouds for him (maybe awakened he will produce his own clouds..?).
That's literally the point - he needs a tool to replicate this feat.
Big Mom achieved this feat on her own, with her homies. And it's not like that's all Big Mom can do. Perhaps she can even perform a similar attack like Enel's Raigou? If she can do that, it's a proof that she's able to eradicate whole islands from its mere existence...
Also, add her ability to add souls to every single object makes her feat even more impressive since she also has Prometheus and Napoleon on her side as well.
And Enel's power has even more destructive power and range.
Well, Onigashima is a large island and it was said several times that Big Mom is able to engulf whole islands with weather control as shown in this chapter.
Plus, each individual lightning is quite comparable to the small mountains on top of the skull - we just need a confirmation how strong each lightning bolt is.
Like his El Thor is 10 times as big.
As I explained above, this is not really the case tho.