Lawyers often pay ancillary expenses for their jobs (including hush money), and bill their clients afterwards. In my own life, my lawyer pays my fees to the PTAB and then puts them on my monthly bill. That goes in my accounting books as "patent-related legal expenses," and this is fine according to my accountant - it's a bill from a lawyer, so it's a legal expense. I don't even know how much the PTAB bills me - the line on my itemized bills is a lump sum that includes administrative work in that line item (and as I understand it, the administrative work is actually quite expensive for a patent).

I think classifying this as "breaking any campaign-finance-related law" is a little bit of a strawman based on the fact pattern. It's one thing to go after someone for giving/accepting donations that are clearly illegal, but it's another thing to go after them for classifying hush money paid through a lawyer as a "legal expense" rather than a "PR expense." However, if New York were serious about justice, they would have had a clearly-politically-motivated prosecutor assign a special counsel to look for malfeasance here instead of running the prosecution himself.

Also, you should read the book "3 felonies a day," and it will give you more context on how much gray area there actually is in most crimes. The thesis of the book is that there is enough of a gray area that the average American commits 3 felonies a day.