Legacy tools like iRemove Tools 1.2.8 became popular because they targeted the specific vulnerabilities inherent to the A5 chip and early iterations of iOS 9. How the Legacy Bypass Process Works
Also, note that Iremove Tools is not endorsed by Apple. Using it voids any remaining warranty (irrelevant for iPad 2) and may violate Apple’s terms of service. Iremove Tools 1.2.8 Ipad 2