Hello Dave, and welcome to the forums.

It's true that a keyword in the hostname might give a bit of a boost eventually. But you have a new website in Google's eyes, and have just experienced something common with new websites. After early ranking and good indexing (often better than you might expect) it mostly goes away and then begins the wait - and the work of building. I've often called this early period of good rankings the "honeymoon". It can take 6 months or more to get firmly established.

And let's take this a bit further. Launching 1,000 subdomains (hostnames) at the same time might easily look like a spammer's footprint. A year or two ago, there was some particularly widespread spam that used this approach.

Google expects that each subdomain will have substance - enough to be worth a separate domain name. If your subdomains are not of that nature, then you might be better off using directories and just one top level domain. Having the keyword in a subdomain is not a silver bullet for good rankings today - at least not on its own.

Thanks Tedster! I really appreciate the advice.

I'd appreciate some comments about how does actually Does Google consider subdomains nowadays. My concept this far was avoid subdomains. But I'm seeing more good serp on subdomains (even from sites I specially don't consider any good at all) seems like Google is rewarding that keyword at the very very begining of the url

IE: mystuffedkeywordsubdomain.example.com