The five growth strategies are high-touch sales, paid advertising, intrinsic virality, intrinsic influencer incentives (Twitch!), and platform hacks.
Emmett forgot to include hot tubs ;)
I think that last one "platform hacks" may be the most crucial now. Even more so than influencer monetization. If you study TikTok user growth it wasn't just mobile video content creation tools and algortihmic ML assisted curation. It represents a foundational change in the way we transmit ideas via memes. A visual language that crosses cultural boundaries easily. There is no analogue to the TikTok video "remix" found on any other platform.