It was because it was a three-way agreement—four, in many ways—between the foundation; myself, representing the Trudeau family; the Université de Montréal; and the donors.
The main reason I signed is that Morris asked me to. I also had signing authority at the time. I was regularly signing cheques at the foundation.
I imagine I could have given a procuration to Morris to sign for the family, but it was his suggestion for the views of the ceremony and for honouring these men. By the way, I still have no reason to believe their motives were not honourable.
That's why I signed. It was in that capacity as a family member giving the permission to use the name.