>In 2001, Naspers made an early, successful investment of US$32 million, in Tencent. As of 2018, Naspers had approximately a 31 percent stake in Tencent, becoming its largest shareholder
The issue OP is bringing up is how their market cap is so small. 18% of $775B is more than $100B. It also means everything else they own is worth negative technically.
https://en.wikipedia.org/wiki/Naspers
its probably because of their early investment in Tencent.