50% of any large tech company are not engineers but people working support processes. Think lawyers, HR, controlling, compliance,...
Now assume a third of the tech half is required to keep stuff running (sys admins, SRE, devops), one third doing the actual developmemt and one third make sure the app is actually aligned with user interests (testing, ui/ux, security)
Split the app teams by platform and you end up with roughly 15 iOS/Android Devs.