on the other hand a whole lot fewer kids are killed by chickenpox.

Although not common among children, the rate of shingles in United States children has been declining since the routine varicella vaccination program began. Like the wild-type (natural) virus, the attenuated (weakened) vaccine virus can reactivate and cause shingles. However, children who get the chickenpox vaccine appear to have a much lower risk of shingles than children who were infected with wild-type chickenpox. Vaccinated children are less likely to become infected with wild-type chickenpox virus, which is more likely to reactivate as shingles compared to attenuated vaccine virus.

One popular explanation, now thought unlikely, is that the increase in shingles might be related to fewer chickenpox cases in United States children due to widespread vaccination against chickenpox. Some people suggest that chickenpox boosts a person’s immunity to the varicella-zoster virus (VZV) and reduces the risk of VZV reactivating as shingles. Therefore, less children with chickenpox could theoretically lead to an increase in shingles in adults. However, this proposed explanation seems unlikely based on two CDC studies which found that shingles rates:
started increasing before chickenpox vaccine was introduced in the United States, and
did not increase faster after the routine chickenpox vaccination program started.
Other countries without routine chickenpox vaccination programs, have observed similar increases in shingles rates.

The CDC seems to be making a pretty good case.
https://www.cdc.gov/shingles/surveillance.html