AppleInsider:

When Adobe InDesign was launched on August 31, 1999, it was aimed at precisely one rival, the then immensely successful QuarkXPress. Yet really the whole development of this page design software is the story of rival companies fighting. There was Quark and Adobe, but also Adobe and Aldus —and Adobe and Apple.

Us oldtimers remember back in the day when QuarkXPress ruled desktop publishing but due to a lack of competition (among other things), Quark rested on its laurels and became a customer hostile company. It opened the door for Adobe.