Why can't Scholastic CEO leave his estate to his friend and not his sons?

In June 2021, the sudden death of Richard Robinson caused a shock to his two adult sons. The reason for the shock is that Mr. Robinson was the CEO of Scholastic Publishing and he left his entire share of the company to his friend and co-worker, Lole Lucchese. His share is worth $1.2 billion, as the company famously published millions of children's books including the Harry Potter series and the Goose Bumps series. 

I'm sure his sons had expectations of being very rich one day, thanks to their inheritance. Now that it hasn't worked out that way, his sons are apparently "exploring their legal options". In other words, they are shopping for lawyers who will find ways to pry some of the money away from the named beneficiary, no matter what their father wanted.

This case bothers me. Why should his sons, who are both adults, both able-bodied, and both independent of their father, assume that they should inherit his estate? The woman he left it to was, according to some reports, a love interest of Mr. Robinson, We do know for sure that she worked in his company in key roles for 30 years. He described her in his will as his "partner and best friend".

Why should he not leave his company to someone who knows the company, has proven her ability to run it, has worked hard alongside him, has shown him personal loyalty and has brightened his life?

So far there has been no suggestion that there was anything wrong with the will itself, made in 2018. Nobody has suggested that Mr. Robinson lacked capacity to understand the will or that Ms. Lucchese forced or unduly influenced him into making the will. His sons have only said that the will is "shocking" and "surprising", To them, I'm sure it is. To those who run the company, maybe not.

The case is not in Canada, so I don't pretend to know all of the laws and rules that will apply to the will and the litigation. 

The reports that I've read have said that the sons are hoping for a collaborative approach to settling the estate issues. As far as I can tell, there is no estate issue except that their noses are out of joint that they are not now multi-millionaires overnight. So, to translate their intentions, it appears that their approach will be "give us several million dollars each and we'll go away. If you don't, we'll sue you and drag it through the courts and cost you millions anyway." Most people would take that deal just to have a peaceful life, but we'll see what happens.