pls see below picture, and https://math.stackexchange.com/review/suggested-edits/1725174. $P(M_2, C_2)$ can't equal both 0 and 1/3. something is wrong!
Math.SE works a bit differently than other SE sites you might be used to. I haven't found it written down very clearly, but my experience is that there is a general community wariness about making substantive edits to posts written by others. If I understand it correctly, the concern is that substantive edits might deviate from the intent of the author or might introduce inadvertent errors, and that it can be very hard to review such revisions to check for inadvertent errors, so the pragmatic solution is to err on the side of rejecting such edits. As far as I can tell, this is not a written rule, but it is a community norm that has evolved.
I can understand your perspective that an edit is better than a comment, when the fix is clear, but I hope you can also appreciate the other perspective. I hope this has given you a better understanding of what's behind the site's standard practices and expectations, so that you can figure out how to work within site culture rather than against it.
In your case, while I haven't reviewed your proposed edits, it looks like some others have suggested that your edit did introduce at least one typo. So, this is a good illustration that the concern about introducing new errors is valid.