"But even if owners ultimately repay the taxes they skipped, deferring payment of those taxes for years, sometimes decades, essentially amounts to an interest-free loan from taxpayers. An owner could reap huge gains by investing that money."

"If owners die while holding their stake, as many do, the tax savings may never be repaid. And their heirs can generally restart the amortization cycle anew."

These are each clear loopholes. The first sentence is about how time value of money matters when talking about billions of dollars. The second sentence gives you an idea of why it was so "important" to weaken the Estate Tax in 2017.