Fast growth usually leads to lots of inactive members. Great if you want to brag to your boss and colleagues about how many people have joined your community, useless for all other purposes.
Slow, steady, growth is much, much, better.
When you grow slowly, you can spend more time converting every newcomer into a regular member. You can personally welcome them. You can introduce them to the community. You can spend time engaging with them and making sure they make friends in the community.
You can do all the things tat keeps members active.
Only a tiny miniscule of communities have more than 1000 active members. You can beat this number, within a year, by growing by 3 members per day.