Reviewing the effect of the Iraq war on the Syria debate, Nikolas Gvosdev tries summarizing the thinking of at least some Syria hawks:
Many of those strongly in favor of the United States taking action in Syria, in contrast, were supporters of the Iraq war (at least until, for some on the Democratic side of the aisle, conditions deteriorated in the aftermath of the successful march on Baghdad). Some concern has been expressed that failures in Iraq should not be used to justify non-intervention in future conflicts. In other words, the wrong lesson was learned. Removing Saddam Hussein and trying to create a democratic successor state was not in and of itself a bad idea—it was how it was executed. Having learned from those mistakes, the United States would be in a better position to avoid those pitfalls in Syria. If the dream of creating a democratic, pro-Western state on the banks of the Tigris and Euphrates was not achieved, at least the concept—that U.S. power, properly wielded, could bring about the positive transformation of a Middle Eastern state—could be validated in an intervention in Syria.
Some Syria hawks may be thinking this way, but I’m not sure that there is that much interest even among Syria hawks in trying to “bring about the positive transformation of a Middle Eastern state.” While their goals of regime change and opposition victory may be very ambitious, Syria hawks seem to have little interest in the positive transformation of Syria. Their principal concern seems to be the destruction of the current regime, and just as in Iraq there is little or no attention paid to what would be done to reconstruct a working Syrian government once this is achieved. Democracy promotion was always the fallback excuse for the Iraq war when the original justifications proved to be entirely false, but in the Syrian case most hawks are not even trying to pretend that intervention in Syria would have much of anything to do with promoting democracy. For many Syria hawks, the reason to intervene in Syria is not to promote a more liberal or democratic political order. Indeed, some Syria hawks may understand that any post-Assad regime will be illiberal and majoritarian, but this doesn’t stop them from wanting to bring it to power.
No, the reason most Syria hawks want to overthrow Assad is to reduce Iranian influence, and there’s not much more to it than that. Even if that means that the conflict is prolonged and made worse, or if it means that Syria’s minority communities are decimated or expelled from the country, most Syria hawks apparently still want to intervene. Most Syria hawks are obsessed with Iran and they insist on viewing all other policies in the region in terms of whether it hurts Iran or not, and the desire to hurt Iran seems to be so great that there is not much thought given to the tens and hundreds of thousands of people that will suffer or die as a result.