Airaku
Stray Jedi
No. The viral leak in Racoon City wasn’t the fault of Umbrella. The hunk infiltrated the underground laboratory in a bid to steal samples of the G-Virus. Unfortunately for them, they were killed by a mutated William Birkin and the samples crashed to the ground and thus leaking the virus into the sewers. The rats licked up the G-Virus, became infected, and then carried it out of the sewers onto the City streets where they proceeded to bite people and infect them too.
Hypothetically-speaking, if the T-Virus had not leaked in the Train and spread across the Forest, Albert Wesker would have been working in the Mansion laboratory at the time when the City became infested with zombies. All the S.T.A.R.S members would be alive and called in on an emergency – including Albert Wesker. They would have had to evacuate the City along with the other survivors and relocate to a different Town. And surely the S.T.A.R.S could have continued their operations under a different Police Station. So it would no longer be the R.P.D S.T.A.R.S, but something else (insert the name of an American Police Department) S.T.A.R.S.
Albert Wesker would also have continued working for Umbrella and transferred to the nearest Facility.
Now, I say this because in the canon story he didn’t come up with his “back-stabbing plan” until he saw an opportunity for a win-win situation. The viral leak in the Forest gave him his opportunity to dispose of S.T.A.R.S – and steal the combat data. Albert Wesker “gave up” his humanity on this premise. He needed to make it look as if died that night at the Mansion, both to avoid the authorities and to escape from the clutches of Umbrella.
Alas, James Marcus is responsible for everything!
I agree partially with you. What you say about the Rats is technically true. Though in the case it was an accident all around, but yes, you are technically right.
As for the rest. Albert was formulating his plans long before the train incident. S.T.A.R.S. was formed 2 years prior to the event. As for James Marcus, he did indeed plan his revenge to destroy Umbrella, and he succeeded in doing so. He started the chain of events that lead to Umbrella's downfall. However it all traces back to Umbrella, and Spencer. Marcus was one of the founding fathers so he put himself in that situation, this much is true, but there were events that led up to this.
I cannot stress enough that you read the Wesker Reports, especially the second one. A lot of what I mentioned about Albert is clearly stated in them. Which is cannon and explores his backstory. It also explains the truth behind Lisa Trevor and also serves as a backstory for William Birkin as well.