A lot of their software was from acquisition even the original iTunes
Absolutely.
The biggies ...
Mac OS X - NeXT
Apple Silicon - PA Semi
Plus, all of the good stuff.
Final Cut Pro/iMovie - Macromedia
DVD Studio Pro - Astarte
Logic/Garageband - eMagic
iTunes - SoundJam
Keynote - Lightstream Design (NeXT Developer)
Pages - Claris
Siri, App Store, Face ID, Touch ID, iTunes Match, Maps, etc. were all acquisitions (or made up of) too