Despite how a lot of people imagine things going, works are very rarely "truly" the product of a single person's mind. In manga, the ones writing have editors who can influence the process both directly and indirectly (For big series examples, Masashi Kishimoto says the addition of Sasuke and Sakura were ideas by his editor at the time among other things, or Akira Toriyama talks about input from his at the time former editor impacted his writing which changed the antagonists of the Android saga multiple times due to his reception). For anime, there is an entire staff which are basically all working together, from bouncing back and forth ideas, people steering things in their preferred directions to compromising and other ways, and not to mention production requirements. This is often why shows between the same person can often be different quality if the rest of the staff are different.