Jerry's plan was to hope the deadline would add pressure to McCarthy and get him to take a deal on his terms. I think the fact there was so much interest from other teams interested in interviewing McCarthy surprised Jerry. Jerry suddenly lost his leverage and McCarthy, sitting on a pile of money already and knowing he may have other options, waited out Jerry.
This also highlights, yet again, how unfit Jerry is at running this team. First, the decision on McCarthy should have been made weeks ago. And if the decision was that you wanted him back (which seems to be the case), then you get that deal done immediately. Playing chicken with a HC is absurd. The most profitable franchise in sports haggling over years with a coach you want back and then lose when he calls your bluff? Even more absurd. What a disaster.
Now, if the decision was you didn't want him back, feelers should have been sent out immediately to names like Belichick, Vrabel, etc. The worst case scenario is deciding you wanted McCarthy back, play games with him to then lose him at the last second over your stupid attempt to leverage him into a real favorable deal for you and then have some of your better targets already be far along (or hired) by other places.
It's no surprise that's the path the Cowboys chose. Buckle up fans, it's going to be another in a string of disasterous offseasons.