By creating sockpuppet accounts, you can fake more activity in discussions. This encourages real users to participate. Repeat until there are enough real users to sustain a community without sockpuppets.
Reddit did this, as they said in this interview. Others confirm the approach.
Lemmy is already very active. I asked people their favorite video games over at [email protected] a few days back and I’m still getting replies. I also agree with others who say this is an unethical way to do things. If you make interesting posts you will be rewarded with interaction and activity.