I genuinely don't get any of the transformations for the entire series except maybe Wesker. There is a 99.9% chance you are going to turn into some horrible monster. Why would anyone voluntarily do it?
It's like the J'Avo- why would a mercenary force volunteer to turn themselves into some sort of variation of crab creatures?
All of them have unique reasons as to why they transform according to the situations they found themselves in.
Alexia: Could revert to human form at will, until her second mutation caused by damage and the virus being unable to keep up with the necessary regeneration.
Morpheus: Was dying. Injected himself with the t+G-Virus to save his life knowing that it didn't decrease intelligence and made the host practically invulnerable.
Birkin: The G-Virus was incomplete and Birkin was done for. He gambled on becoming the virus' intended mutation, a G-Human, a superhuman. It failed due to being incomplete and going out of control.
Wesker: Overdosed, but would've metabolized and reverted to human form until he was damaged so much the virus began tearing his body apart, unable to keep up with the regeneration necessary.
Sergei: Had no chance of beating superhuman Wesker. Decided that becoming a monster but maintaining his cognition was his only recourse.
Piers: Lost his arm, mentor was dying, injected himself "for the BSAA, for the future."
Carla: Was shot and fell, thus dying. Injected herself to prevent death knowing she'd still maintain at least some cognition.
Ryan Howard: Cornered by agents, injects himself knowing he faces either death or life imprisonment. Also overcome by grief and shame.
In regards to the ELA mercenaries, Carla claimed it was a "nutritional supplement" that would boost combat prowess. The ELA was trying to end the civil war in a decisive strike, so they took anything they could get. She'd also supplied the Ogroman B.O.W., so they trusted her.
That's a one trick pony though- why would anyone in China still inject themselves with the C-Virus 6 months after what happened in Eastern Europe?
Nobody in China injected themselves. Carla offered young and healthy men from the poor population money in exchange for participating in "
medicine experiments something or other." Then she injected them with the C-Virus.
Seriously, tho, can News Bot or someone explain why Leon and Helena weren't affected by the Lepotitsa gas in Tall Oaks, the plane and Lanshiang? Yeah, I know — "gameplay, lol" — but they're usually more attentive to detail than that. And I vaguely recall there being an explanation, but I can't remember what it is.
Are they on a cutting-edge vitamin regimen? Does their hair product deflect environmental contaminants? Are they holding their breath? Are they infected with a virus that produces plot armor antibodies?
Helena was locked up in an isolated room by her fellow
Secret Service agents for ranting and raving about the President's impending assassination. We don't know where Leon was, but he'd just turned up in the room at the beginning of his campaign (you see a brief shot of his shock upon entry) so presumably he was in the same situation. Almost everyone else apart from a few students were outside, where the gas permeated. A few ran back inside.
Since there's a few people here discussing the series story, I'll throw in my two cents. The story going bigger is leading it to being more ridiculous than ever, true, but my biggest problem is the villains. 6's villains were an absolute joke, I think. Simmons and Carla were easily the worst/ dumbest villains in the series history, and "The Family" and "Neo-Umbrella" were like something straight out of bad fan fiction. They just didn't live up to either Wesker or the Umbrella Corporation, and without great antagonists, I think the series feels a bit aimless at this point. We really need a new "Big" bad guy (or corporation) that's actually cool/threatening , and sticks around for more than one game. I feel like it would really add a lot to the overall story.
Simmons is a great villain, but he's tied to Carla and thus dragged through the dirt.
The Family are fine. A secret cabal tied to an ancient family. It's cliché, but not illogical or silly, and different enough from iterations of this type of organization in other media. They don't contradict or interfere with established lore either. I think it was created so that the writers could take the easy way out on the dark side of the U.S. Government, without portraying the U.S. Government as outright villains. It's basically the same organization seen in The X-Files (Syndicate), Deus Ex (Illuminati) and The Blacklist (Cabal).
Neo Umbrella was never meant to replace Umbrella. It was a faux organization created by Simmons using The Family's resources in order to perpetuate bioterrorism and maintain the U.S. as the dominant superpower, using his position as National Security Advisor to strike down incidents caused by Neo Umbrella as a show of power on the global stage. The reason it's called Neo Umbrella is to get people in the BIO world to think about Umbrella and exhibit the same sort of primal fear associated with them following Raccoon City. Meanwhile there are plenty of former Umbrella researchers around the world to pin it on.