As someone who was in a non-technology role[1] who has interviewed people for technology roles I think ageism in technology is often inadvertent (I've never heard anyone say "Candidate X is too old for this position") and "shows" itself more than other areas because technology moves so fast. As people move up in an organization there is less need to hone their skills. "Old school" investment managers I have worked with still manage to the 60/40 rule. Similarly, a bank I worked for had a CTO who was probably top-notch at server security in the 1990's but completely resisted any SaaS that used AWS because of "security concerns." Instead of learning how to assess whether the way a potential vendor has configured AWS posed any risk to our company he just turned them away. He didn't understand AWS and had no interest in trying to. Because technology advances so quickly the CTO has been let go (resisting AWS is futile) while the 60/40 guy will probably continue to mismanage money for his clients until he decides to retire in the next 2-5 years.

[1] Attorney but also happened to wear Chief Info Security Officer/Chief Privacy Officer hats