I think Kasich and Cruz were natural allies to siphon votes from Trump. Together they cover a wider spread of appeal than either alone would present.
I think the powers that be flinched at spending another $50,000,000.00 or so for more goose egg results. Closed checkbooks meant closed doors on those two ankle biter campaigns. The war to thwart Trump will be conducted on other fronts now. The primary has been ceded.
These two might not physically continue to publicly campaign, but there is nothing to stop them from continuing to buy delegates underground.