It's really simple, this is VC pyramid scheme at play. Say you put $100M into a company at $1B valuation. A year later you put $250M at a $3.25B valuation. Your $350M is now valued at made up $580M. When the company later sells for just double, $7B, your $350M became $1.2B.
Yikes. Sitting at a WeWork right now... Love it, I often have an entire floor jus to myself. Many locations are ghost towns, some have entire floors shut down.