My wife cashed in an RRSP. It was likely set up as a spousal RRSP 15 years ago. The T4RSP was loaded from CRA, however the income was allocated to me? How come?

Have you contributed to a Spousal RRSP within the last three years?

Yes.  But not the one that I was cashing in?  I contributed quite a bit to one last year.  She also cashed one in.

When you withdraw funds from a "Spousal RRSP" if you have contributed to ANY spousal RRSP within the last three years, the funds withdrawn are reported on the Contributor's (you) tax return, and any tax withheld is reported on the Annuitant's (your wife). 

https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/rrsps-related-plans/making-withdrawals/withdrawing-spousal-common-law-partner-rrsps.html