This chart may help https://www.irs.gov/retirement-plans/required-minimum-distributions-for-ira-beneficiaries

From your statement - Died  before required beginning date & beneficiary of the IRA was a trust - With that "Take entire balance by end of 5th year following year of death"

Now the question is who owes the tax on the IRA? The trust was the beneficiary of the IRA, but the nieces are the beneficiaries of the trust. 

I like asking questions.