The main reason for the larger and more prominent rear-camera bump of the 14 Pro/Pro Max is upgrading the wide camera to 48MP (vs. 13 Pro/Pro Max's 12MP). The diagonal length of 48MP CIS will increase by 25-35%, and the height of 48MP's 7P lens will increase by 5-10%.
The schematics show a camera bump that measures 36.71mm x 38.24mm.
Kuo has repeatedly predicted a 48MP camera for the iPhone 14 Pro, saying that "the camera quality of the new 2H22 iPhone will elevate mobile phone camera photography to a new level." Additionally, the analyst believes that the new smartphone will be able to record 8K that is "more suitable for AR/MR devices" and that will "enhance the AR/MR user experience."
TrendForce has also predicted a 48MP for Apple's next generation flagship.