Delighted to hear you enjoyed it so much, and sorry that pesky memory issues stopped you from enjoying the ending when you were so close.
As for the main menu, the camera transitions are done very easily using Cinemachine in Unity. You can install the package, and add the Cinemachine Brain component to the main camera, then make separate gameobjects with Cinemachine Camera components on them, and each time you enable / disable a camera it automatically switches, you can then control the priority and whether the camera should hard cut or smoothly transition. The main camera sequence that takes you into the game once you click the start button, is done using a Cinemachine camera that follows a spline like its on a rollercoaster track. It's the first time I've tried it and will definitely go back to experiment some more.
Thanks again for playing!