This is wild speculation but here's a hypothetical:

If you were the CCP, have decided that war is inevitable, you know Japan (which used bio-warfare on you in WW2) is a key in any battle, and you see that totalitarianism has a systemic advantage in controlling/exploiting Covid - would you be tempted to unleash a souped-up variant at the Olympics?

It would be impossible to pin on you cause it'd be seen as just the latest variant.

The closing ceremony would be the ideal place to seed it.