It's hard to tell which is which and it's probably a bit of both. I don't really understand why whenever the living nature is being explained, it's done in a way that attributes to some design what really belongs to an accident of evolution. Species develop traits continuously and in a chaos, every individual is a mutant, then environmental pressure determines combinations that are most suited to reoccur (through reproduction).

In this case two species found each other. Maybe a few springtails had the genes to detect the smell. Of those, a few found it pleasant, it could be that others didn't. Maybe a few streptomyces had the genes to produce the smell. A happy accident that allowed both these genetic traits to endure environmental pressure.

Producing that smell is 'costly' and doesn't seem to have any other use, so if it wouldn't benefit the bacteria then they would be expected to evolve to not manufacture these chemicals.

Did bees evolve to find nectar or flowers evolve to attract bees? A lot of both.