Scholarship awards more random than admissions?

There could be many factors influencing the situation.

1) What dukes said.
2) Different scholarship criteria in between the schools. For some schools, scholarships are a way to attract students while for some other schools scholarships are need based only. This means that they assess the overall financial situation of the students (based on past salaries, assets and liabilities) and define how much money to give.
3) Some schools may be struggling to get their target yields from a particular group within their applicant pool. Eg: let's say school X wants to have an increase in the number of students with, for eg: IB backgrounds, Russian Language knowledge and 780+ GMATs. They do get the right number of apps. and admit about the right number of applicants from this pool but these applicants consistently choose not to enroll in school X. School X then decides to increase the amount of money offered to students from within this pool. Likewise, they would not offer that much money to the "dime a dozen" admits, because recent history shows them that most of them enroll anyway.

So that's my SWAG* answer to your question.

*SWAG = Scientific Wild @ss Guess