why are they buffing all the ad champs

do all these champs just happen to needs buffs to their damage or is there some big pre-season change affecting them?

do all these champs just happen to needs buffs to their damage or is there some big pre-season change affecting them?
They're going through and buffing everyone. The change is the old runes are going away, and the stats that champions relied on from said runes need to be compensated for in some way.
Yasuo has been getting nerfs pretty much every patch, graves isn't very good anymore.. not the best in any situation.., other than that some of them dont need it and some of them need some minor buffs
In context to most of those champions, they were shit or at best average for months when they recieved those buffs.
Riot does random buffs to shift balance slightly all the time. They've definitely overshot it with champions like Jarvan and Fiora but most of those champs are still manageable even with a bit more stats.
If I wasn't lazy I'm pretty sure I could pick a class like mages and point out a list of them that got randomly buffed over the past year too, maybe you have a point that they're doing it to bruisers more but we are in a tank/support meta where bruisers have to work to kill their targets if its not early game.