The world of Resident Evil is a pretty terrible place, as massive bioterror events just keep breaking out. The penultimate villain behind most of the problems in Resident Evil is the Umbrella Corporation, known for its iconic red and white logo.
Like many villains in media, Umbrella continues to make what seems like the worst choices, over and over. After the Mansion and Raccoon City incidents, the company didn't learn its lesson and continued to develop BOWs and monsters.
Of course, Umbrella needs to keep doing evil things for the Resident Evil series to keep going, but there area few in-universe reasons the corporation keeps going as well. Here's why Umbrella keeps making monsters.
Umbrella Has a Lot of Motivations For Making Monsters
Umbrella's original plan in developing the T-Virus was to sell it to militaries and governments, as it could be used as a deadly battlefield weapon. The virus could be spread simply through bites, meaning soldiers wearing gas masks and protective gear wouldn't be safe. Selling these weapons would result in incredible wealth for Umbrella, as well as a degree of control and influence over the biggest governments in the world. Early incidents, like Racoon City, were actually orchestrated by Umbrella to gain test data.
While these may have been the initial motivations, later games in the series bring new revelations. In Resident Evil 5 flashback scenes and reports show Albert Wesker talking to Oswell Spencer, the founder of Umbrella. Spencer invested in a eugenics program, in the hopes of finding the secret to eternal life. Spencer wanted to become a god, and wipe the Earth clean to create a paradise that he'd rule over. To that end Spencer and Umbrella continuously ran experiments on new viruses and parasites, trying to find some unknown secret.
Eventually, the United States government learned that Umbrella was behind the Raccoon City incident, and while the company was under severe scrutiny and investigation they began selling BOWs to terrorist organizations in an effort to bring in cash that would keep the company afloat. It's important to note that Umbrella was dissolved in 2003, roughly one year before the events of Resident Evil 4 and Resident Evil Revelations. Wesker would then continue his own work to try and become a god, while various terrorist organizations began to use bioweapons in their attacks. Still, Umbrella was the spark that lit the flame, and their influence can be felt throughout the entire Resident Evil series.