Io is the result of an early study on putting a human conscious in a reploid body. They volentered because the pay was high (considering well, you are giving up humanity for the sake of science), and they needed to pay off some bills + fund a project of theirs.

The company that ran the study was known for being very eccentric, directionless, and at times ethically questionable. So much so that the study was cut short after less than a year due to a lack of funding and a few lawsuits. And for Io... welp, they got some compensation at least but they were left on their own.

Io initially got some IT training while they worked on a pitch for a book they were working on. While it did get picked up, the book deal ended up falling out sometime during the events of X6. (Io was writing a drama and the publishing house was uneasy about 'morally ambiguous reploid characters that could be interpreted as mavericks'). So sticking to IT it is.

They had bounced between multiple IT jobs; notably one at a print shop, and one at an (unnamed) tech company. They were fired from the latter after they went on strike. This eventually lead to...

Hunter Base IT era

At the time of hiring (some time after X6), Hunter Base was understaffed and comissioning new reploids was out of budget. Io managed to snag a job from a listing for the tech/R&D department. For the most part, Io blends into the woodworks and does computer maitnence, data organizing, etc.

They become head of the IT department... because no one else wanted to do it. A TL:DR, Douglas wanted to split the tech department into smaller sub-departments and they were the only one who wanted to stay in IT ("I'm honestly suprised I got the offer in the firstplace."). They've somehow managed to keep things together despite the department being critically understaffed.