Here is my take on trying to explain what the heck is going on in the opening scenes of Tenet.

Reddit was a great resource for discussion and there were a lot of great insights.

My approach was to try to keep things as simple as possible without having to bootstrap the entire thing.

The terrorist attack was real.
The CIA exchange was real.

Sator used his knowledge to set up a heist to lift the algorithm from the CIA.

Having observed The Protagonist's willingness to sacrifice himself, Tenet( or Future Protagonist) ensures his pill is fake so he can be recruited and continue the chain of events