It can’t be political. Every day that goes by without someone claiming responsibility, the probability of it being political decreases exponentially.
But at the same time, this doesn’t seem like the work of a lone wolf. Lone wolfs usually try to kill people. And almost invariably they fail miserably, killing practically no people at all compared to the number of people that would have been killed at the hands of someone smart or competent with a weapon. And bombs stand out as being difficult for lone wolves to get right. For a lone wolf to build a working bomb and detonation system and have everything work perfectly the first time would be the exception, although not the only one.
This was done by one person. Not a typical lone wolf but someone who was smart and methodical. And I would guess he was in the vehicle when it exploded. He was either insane ala templeOS, had no motive ala Mandalay bay, or a disgruntled employee.