My wife of 30 years cheated on me for 11 months

My wife of 30 years cheated on me for 11 months that I know of. Probably longer. We had good jobs and made plenty of money. We had a special connection and a great marriage. Raised 2 boys together and got along most of the time. We promised each other if it came down to infidelity we would let each other know and go our separate ways. That didn't happen. She lost her job while I received a healthy inheritance when my dad was murdered. She never looked for another job thinking I could take care of us both. That was not the case. For it all to work financially, she needed a job while i retire. She never went back to work and depleted my bank account. She stole money from me, lied to me and was not loyal. What makes someone change so drastically to do all those things to me?