Leaving aside for the moment that the whole Jack Ryan mess was entirely avoidable, it just isn't true that there wasn't anyone to run. But the national party has made it clear that they're writing off Illinois, and therefore weren't going to put any money into the state. Under those circumstances, qualified candidates wouldn't take on the job because there was no financial support.
Keyes wasn't asked because of his conservative principles. He was asked because he will attract out-of-state money.
One would assume, considering that they've put in place an almost 100% pro-abortion speaker slate for the convention.
But I guess the good Lord had other plans.