One of the biggest questions Resident Evil fans have regarding the Netflix TV series is how Albert Wesker is somehow perfectly fine! For viewers of the show who have little to no knowledge of the games, this won't mean much. In the games, however, Albert Wesker is one of the most iconic Resident Evil characters out there. Aside from the main protagonists like Chris Redfield and Leon Kennedy, Wesker is a diabolical villain who causes a lot of violence and chaos. He's a pretty critical part of Resident Evil lore and has crucial connections to Umbrella, some of which is seen in this very show.
With that said, Wesker died fighting Chris Redfield in Resident Evil 5. After taking a strain of an Umbrella virus, Wesker mutated and became a disgusting, giant monster which allowed him to make his final stand in a volcano. While sinking into a thick pool of lava, he made one last attempt to take Redfield down with him, but with the help of Sheva, the two heroes obliterated him with rockets. If he survived the rocket blast, he was surely killed by the lava itself after Chris and Sheva escaped. So, how is he alive in the TV series? Well, he's not… technically.
The original Albert Wesker made clones of himself without the direct approval of Umbrella. This caused all kinds of problems, leading Wesker to kill one of his clones while escaping Umbrella agents. The clones were made to be super smart and aged up to about 20 years old six months after birth in order to effectively do his bidding. The real Albert Wesker is actually dead, just as we saw it in Resident Evil 5.
Umbrella made a deal with the Wesker we see in the show to give him a real life in exchange for his knowledge and brain, essentially making him the smartest man at the company. With that said, Wesker's rapid aging created problems inside his body, giving him a fatal illness if not properly treated. To cope with it, he created two daughters and regularly uses their blood to help with his condition.
There is also one other clone named Bert who is a much more child-like version of Wesker. He's incredibly efficient at hand to hand combat and super smart, but he lacks social skills. Not only does he behave like a kid, but, as demonstrated by a scene in an Olive Garden, he doesn't know how to act around other people or interact with them.
With all of that said, Albert Wesker isn't really alive, at least not the one we're familiar with. So, for anyone expecting him to appear in the games again after this, you probably shouldn't unless Capcom finds a different way to revive him. It's an interesting way to bring back a beloved character while also putting a new twist on him, but the show has had an overall mixed reception from critics and fans alike.