Newsletter growth suggestions

For context
I currently am running emailemu.com and run a newsletter tied to the product.

I see all of these posts with people who have grown their newsletters to 5-6k in a few months and I am wondering how?

Where have people found success getting so many people to join their newsletters within a few months?

Are there any people on here that could provide suggestions?

I am targeting mainly marketers currently.

any tips would be wonderful!