There were no bank failures in 2018, which is the first time that this has happened in 12 years, and only the third time that this has happened since the founding of the FDIC:

In 2018, no FDIC insured banks failed. This was down from 8 in 2017. This is only the third time since the FDIC was founded in 1933 that there were no bank failures in a calendar year.

For the life of me, I have no clue as to why credit union failures have outpaced those of commercial banks for the past two years.

Any suggestions as to why this has happened?

At the peak of the crisis bank failures were outpacing credit union failures by about 9 to 1, so this flip is rather perplexing.