Why? They were abusing LinkedIn's service by competing with them.
LinkedIn took the time to speak with them, evaluate the situation, and then make an informed decision about whether they wanted to support their appropriation of LinkedIn's data.
It's crappy human behavior, which is not to say 'bad business practice', to pretend to work with someone and support their efforts for 2 months, and then summarily shut down their business simply because LinkedIn made an 'informed decision' that 'we don't owe you anything.'
Let's not confuse the fact that, although businesses certainly have a right to defend their own interests any way they see fit within the law, that has absolutely no bearing on whether or not the community they conduct business in will call them out when they act in a basically unkind or deceptive manner.
The former has to do with business, fine print and the dog-eat-dog, watch-your-back world of modern commerce. The latter has to do with basic human decency, trust and the goodwill of the community you do business in.
"It's just business" is all well and good, but don't get butt-hurt when the community that you work with looks at your behavior and says, "it sucks that you did it that way." That's just the cost of "doing business," right? Suck it up and take it.
LinkedIn took the time to speak with them, evaluate the situation, and then make an informed decision about whether they wanted to support their appropriation of LinkedIn's data.