Many of our great presidents were deeply flawed like this. Teddy Roosevelt was a nincompoop when it came to business and the economy: he savaged corporations, but in the process, research has shown, he severly damaged "small businesses." Great on foreign relations and patriotism, he nevertheless stifled economic growth in his administrations.
Bush was good for two big visions: defeat the Jihadists and revive the economy. He apparently doesn't have a third in him. Ok, neither did the great god Ronald Reagan, who gave out our first amnesty, and who allowed welfare spending to rise and who allowed the federal government to grow under his watch. But he defeated the Soviets and got the economy out of the doldrums.
Presidents, like most people, can only do one or two things really well. After that, it's mush. If you don't believe me, watch me play golf some time.
He knows our primary threat is Islamic WMDs, which means we just can't afford to take our eyes off the ball in terms of collective focus.
Illegal immigration has to be brought under control at some point, but right now it's like any triage situation: Iran needs immediate attention right now, while Mexico only needs to be managed so it doesn't fall off a cliff. That means continued taxpayer support illegal immigration in the short-term.