conjunctions - Omission of "but also" in "not only ..., but also ..."

I've seen some topics related to this correlative pair 'not only..., but also ...', but I'm still not quite sure if it's correct to use a comma without any conjunction in the following construction:

"The American commoditization of time not only serves as the basis for a "time is money" mentality, it can lead to a fixation on timelines that plays right into the hands of smart negotiators from other cultures".

In this excerpt, the comma between 'mentality' and 'it can lead' joins the two independent clauses without any conjunction. Can we use commas to join two clauses without any conjunction?

I was thinking that the conjunction 'but' should separate those clauses, because 'not only..., but also ...' is a correlative pair, so it is always used as a set. Am I wrong? Or I guess there should be at least a semicolon between them.