Resident Evil: Albert Wesker Explained
The Puppet Master
Wesker maintained the illusion of death for a surprisingly long time. With only getting his hands dirty during the Rockford Island siege and the raid on the Caucasus laboratory. Working for his own means, he would employ the services of Ada Wong and Jack Krauser, a former soldier of the United States Military. And as the ’90s came to a close, a new Century dawned, this is where Wesker would truly rise to power.
Pulling strings, he would go on to acquire a sample of the G-Virus, T-Veronica Virus, but needed more in the aim to create his final Virus. This meant, that in the events of Resident Evil 4, when the president's daughter Ashley Graham was kidnapped by Los Illuminados Wesker had the perfect opportunity to obtain the Las Plagas Parasite.
Little did Osmund Saddler know, he was just playing into a greater plan that Wesker would eventually act upon. Meaning that all of Saddler’s work with the Parasite would eventually end up in Wesker’s hands, to provide to Tricell.
After Leon S. Kennedy saved Ashley, it all seemed like the mission had been accomplished, but in a matter of fact, they had effectively lost as Wesker successfully received the dominant Plaga Parasite from the dead body of Krauser, no thanks to Ada Wong, who betrayed him and gave Wesker a standard one.
From here he would go onto dissolving the Organisation's leadership, taking over what remained for himself.