Pre production might've started first, but that does not involve developing. Pre production involves hiring the right people for the project, getting funding, getting the right equipment, and much more. It's not quite development yet. Also since Respawn was a new developing company, they had to take longer than other big developers might have had to be able to get a publisher that would want to publish their game. But Treyarch hardly had to spend any time on pre production because they were already a big company, and already had a publisher, employees, proper equipment, funding, and all that a developer needs to begin development. Titanfall might've started pre production first, but Treyarch started development first.