I doubt mama was 'clueless'. She knew exactly the business and way of life her husband led, and her sons had been raised to lead.

Perhaps she decided one day that asking too many questions and attempting to unturn every goddamned stone would make her a pain-in-the-ass. Aside from that she apparently knew to allow herself and her family to be taken care of, hope for the best and look the other way. Michael had to order his wife (Kay) not to ask him about his business. Apparently, Vito did not.

By the way, at this point I must defer to those who have maintained how the novel goes into such greater depth than the film...and with plawrence who says in this thread that you cannot 'divorce' the two (that is, of course once one has actually read the novel). For it is explained carefully in the book how a young 'mama' Corleone comes to the realization and acceptance I suppose...that her husband has stepped over a threshold from regular, honest working family guy to ... well, the Vito Corleone we all know he becomes.

Apple