Oliver didn’t wish to put his family at risk by escaping and instead instructed Talia to pass on a flash drive to Felicity that would reveal what was happening at Level 2.
Talia escaped, and her flash drive helped Felicity, Dinah and Black Siren bring the experiments to an end.
Talia needed help escaping Level 2, which she revealed that Dr. Parker used to conduct twisted psychological experiments on inmates.
Oliver eventually agreed, but requested something of his own in exchange.