How is this containing 'all the while' a fused sentence?

Question

http://www.chompchomp.com/terms/fusedsentence.htm alleges that the following is a fused sentence:

Driving home from school, Brett vowed to protect the fragile ecosystem ♦ all the while the tires of his Cadillac Escalade flattened the toads hopping on the wet streets.

The first main clause is 'Brett vowed to protect the fragile ecosystem,' and the second is 'the tires of his Cadillac Escalade flattened the toads hopping on the wet streets'. Notice that the two clauses run together with no punctuation.

One proposition from that website is to use a semicolon at the location of the square. But why not just a comma? Wiktionary states that 'all the while' is a conjunction. What are the true issues here?

Answer 1

I'm not so sure about the conjuction part.

For example, check this definition all the while.

all the while
for all of a period of time:
There I was thinking you were hard at work and you were upstairs in bed all the while!

Also you could add a comma and conjunction without changing the meaning a lot:

Driving home from school, Brett vowed to protect the fragile ecosystem, and all the while the tires of his Cadillac Escalade flattened the toads hopping on the wet streets.

But otherwise use a semi-colon.

Answer 2

It can't be just a comma because you're connecting two independent clauses. In order to connect two independent clauses using a conjunction (in your sentence, 'all the while'), a comma must be used before that conjunction.