Even ignoring global OS marketshare, iOS app store customers just simply spend a lot more money per user on the App Store vs Google Play (Google's Android app store). You gotta go where the money is to some extent to get paid.
Global revenues on the iOS app store have always been significantly larger than Google play, even with only ~30% of the global smartphone market.
Average amount of money spent means little in the context of parent's comment (revenue for a US company).
For instance, if you're Netflix, do iOS user bring you more revenue in the US ? What if you're Hertz ? What about Walmart or Costco ? The only factor will be how many of your users are on iOS vs android. It's a different story if you're a gaming company and target whales of course.
Even if you're a social media company, where network effect is everything and getting into everyone's pocket matters, you can still go iOS first. Snap ran with that strategy at first, and it hardly killed the company.
Notably, that's a situation that actually matters for cross-compatibility. There's no web client for SnapChat. Hertz & Costco could point Android users to the web with few repurcussions, IMO
This is still about the actual market share. iOS being 55%+ of the market makes that strategy viable in the US. You'd start with android instead if you were to launch in Korea for instance.