I think by "competition", they were referring to Amazon, not Jet. Buying Jet for 3 gigabucks could still be worth it, if it can help Wal-Mart vault into serious online competition with Amazon.
But Jet can only help Walmart compete with Amazon if it has some virtues. And the point is, even if its people are great, they aren't worth $3B. If Jet's technology or brand or whatever are going to help Walmart compete with Amazon, then it's not an acquire-hire.