Because no dark matter got released this time. The particle accelerator doesn't make meta humans; dark matter does. From the first episode:
You can see red waves of energy which were responsible for making meta humans. We know this as dark matter.
Even when Harry was confident enough to restore Barry's power by a second explosion, with the over-confidence of being able to contain dark matter with Eobard's data, there was little leak which hit Jesse Wells and Wally West:
It's again shown red.
When dark matter got released back when team flash tried to rescue the Flash from the speed force and made bu full of metas:
And when the particle accelerator nearly exploded because of Hazard's luck power, we see this:
It's clear that it's full blue and have even no red tint, so no dark matter released. But what really happen is explained well by Cisco himself:
Cisco: What just happened? [EXHALES SHARPLY] The hydrogen electron collision released a charge that temporarily negated Hazard's quantum field.
Cisco: We did it.
Cisco: You did it.
Cisco: How did you know to do that?
Wells: Lucky guess.
That's why no new meta formed.
Sources I took help from:
Wikia links: 1 and 2