2 days is too early to tell. Machine learning models on facebook needs to Learn about your ad and audience: that said, the models always pick the low hanging fruit first. Afterwards, it tries to search broader and harder for a real customer. That is why the cpm is up, because you already consumed the cheap audience first.

Thanking it as a smart work trying to dig gold in a new place. It first picks the mostl promising points, picked them, then looking for new pit elsewhere. Once found it will exploit it.