The thing we don't know is when Witten got the offer. If he truly didn't get the broadcast offer until just at that time, I have no problem with the timing of his exit. Yes, it made things a little harder to adjust draft strategy, but that's life. If, however, he knew some time in advance, that's a different story.
Still, it's not as if the team didn't have it's draft board set where they couldn't have adjusted, and there is no certainty even if the Cowboys knew about Witten in advance that they would have moved up to get Goedert rather than waiting and finding the Eagles moved up. Hell, they might have stuck with Williams anyway.