If Ainsley went mad, Michael would lose another medium, and this also showed Michael's bad luck that slowly haunted him, forcing the angel to react quickly.
Michael's luck was not that good due to karma, but 'thankfully', the one he targeted was Ainsley, and somehow, he didn't 'attack' her, which never triggered another karma whatsoever.
However, to be honest, Michael's journey was not as smooth as what the other people see.
If not for him being slightly unlucky, he would have been able to take Ainsley as his medium way faster than now.
The moment Michael's chibi version appeared in Ainsley's mind, the baby froze on the spot, and the painful expression on her face became even more exaggerated.
The price of a forceful possession harmed both Ainsley and Michael.
Now, Michael was forced to become a chibi not only to prevent Ainsley from being driven mad but also to suppress the backlash of a forceful possession.