Yes, it seems like the light switch flipped in a second and then the person you knew has become the exact opposite (mirror image) of the one you actually knew. It truly didn't happen over night. It was a very, very gradual move towards the light switch being flipped. If you can go back to approximately 18-24 months ago, something began the journey for him. Things began to change in a very subtle way, i.e., so subtle you probably didn't pay much attention to the changes or you chalked them up to a bad day or something else.
The one day, the pod person completely takes over and then the acting out and bad behavior, the MLC lingo begins and then they are gone. Some will eventually wake up and want to return, others will wake up, but also continue some of those traits that they picked up along the way and others will leave completely and be angry and bitter old people in the years to come and....then you have some that continue to be pod people living in their own littles worlds (that is what my xh is doing these days). Unfortunately, they don't snap back into normal mode. It will take months, even years, before they will begin the gradual descent back into the real world and that will be approximately 18-24 months and will happen in the exact opposite way that they left this world.
While he's gone, you, as the mature, sane adult are left dealing w/day to day life. No expectations because they will not always follow through and you will get angry, disgusted and disappointed. While they are gone, come up w/a Plan B, i.e., a back up plan for helping you out as you can't rely on your spouse.
Dig deeper for patience, come here to vent and we will try to help you navigate your walk on the yellow brick road.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.