Sec-Fetch-Mode instead of Preflight

I created login FE and finished it. And as per usual my goto for ajax was Axios. My code is as follows.

const baseUrl = http://localhost:5000/project/us-central1/api

Axios.post(
 `${baseUrl}/v1/user/login`,
 { ..data },
 {
  headers: {
   Authorization: 'Basic auth...'
  }
 },
).then(r => console.log(r).catch(e =>console.log(e));

Now when i try to send request to my local firebase cloud function. I get a 400 bad request.

after checking the request, I was wondering why it wasn't sending any preflight request, which it should do(to the best of my knowledge) but instead I saw a header named Sec-Fetch-Mode. I searched anywhere it's a bit abstract. And I can't seem to figure anything why my request still fails.

Is there anything Im missing in my config of axios?

My FE is running on a VSCode Plugin named live server(http://127.0.0.1:5500)

Also, my firebase cloud function has enabled cors

// cloud function expres app
cors({
 origin: true
})

Any insights would be very helpful.

from Sec-Fetch-Mode instead of Preflight