So you made this change to benefit advertisers not Reddit? That's hard to believe.

CPMs should have gone down, not up, since your inventory was expanded meaning same demand for expanded supply. Y'all should also have reduced the minimum allowed bid down from 0.20 since you were expanding your inventory artificially w/ a coding change.

You should have also expected that CPAs for your advertisers were going to go way down once you removed the ad from it's intended context.

Either the logic driving the changes was weak or your explanation is lacking the whole truth.

I see a business in Reddit who wasn't pleasing it's investors and did something hasty to increase revenue.

There was no official communication of the subreddit targeting change to existing advertisers.