It was to buff Tracer and nerf support characters. They couldn’t just nerf the whole support role while buffing the best character in the game without a bunch of complaining so they tried to hide it but that’s what it ultimately did. The support role lost out on a lot more looking back at the changes and what stuck while the damage role are the big winners of balance ever since the s9 changes.
I will miss 2-shotting more characters with Kiriko or even Illari but I can play the damage role and have an even easier time doing so.