Barry came back because middle aged DC editorial hates anyone who replaced a hero from their childhood. So they wanted Barry not just resurrected, but as the indisputable King of the Flashes like he was in the Silver Age, even though Wally had surpassed him as a character and was selling fine at the time. So they screwed up Wally's solo as they made plans to resurrect Barry, and turned Wally into a Z-list character as soon as Barry came back to avoid stepping on his toes.