Local SEO Question - Ranking with Zero Backlinks?

Currently based in South East Asia and I saw alot of single page services websites (plumbing, electrical, electric fans etc etc) that has close to ZERO backlinks and ranking on 1st page of google.

- No content at all
- Backlinks checked with AHRefs, Majestic and many more. Most websites has less than 5 backlinks.
- Probably 2-3 years aged domains
- Ranking for LOCAL keywords only (Local SEO)

How are they doing this? Are they manipulating the CTR via a CTR bot? PBNs? I have never seen such a clean backlink profile before.

Any insights would be valuable.