How do small accounts grow on X?
Short answer
Through replies. Under about 1,000 followers, your replies are where strangers find you. They're seen inside threads, not pushed to For You.
Grok scores every reply from 0 to 3 and runs an extra spam check on small accounts. A concrete addition, a counter-example or a pointed question scores; "this" or "great post" scores about zero.
Source: grox reply_spam classifier