You might have attended in a different era as well.
I attended a very affluent Bay Area HS (there kind where the VPs and C-Suites of tech and biotech companies sent their kids) and they overwhelmingly sent their kids to top public schools (they were targeting top STEM programs, which by default skewed public excluding Stanford/MIT/CMU/Cornell). A couple of their kids attended CS@UW Madison and most of us applied there as a backup in case we didn't get into one of the T10 CS programs.
This was the early-mid 2010s.
The key thing is going to an elite program. Doing CS at a school like UDub or UIUC means you open the door to VCs, IBs, and Founders who all also attended that elite program (as well as their equally elite parents). You might not get that network majoring in English or Horticulture at either college, but you definetly will if you're in a top program.
In addition, Asian (India, China, SK) Elites target colleges based on how the specific major they are targeting ranks. As this overwhelmingly skews STEM and Business, you end up getting a massive cohort of foreign elites at Public schools.
A lot of this is also because of targeted branding by public unis and regional private schools to undercut the more established private unis like Harvard.
For example, within India Harvard has a weaker pop culture branding and alumni network than a top CS program like Carnegie Mellon, Stanford, UIUC, or UC Berkeley.