As with everything, there are multiple reasons. Resources are one of them, but played a support role instead of primary. The resources were seen as a way to mitigate cost. War is expensive. By using local resources, you don't need to run supply lines and logistics for those resources from depots.

The contractors and privateers saw the opportunity to make money. Think organizations like Halliburton, Raytheon, CACI, and Blackwater. The military uses these companies to fill out roles that are otherwise burdensome for an agency that needs paperwork for everything. The downside is that there is almost no accountability when things go wrong.

The key thing to keep in mind is that these are not wars. Declaring war must be authorized by Congress. Instead, we got the Authorization for the Use of Military Force. This Congressionally-approved law is not against a country. We did not go to war with Iraq nor Afghanistan. We went to war with Saddam, Bin Laden, and "terrorism". This allowed the US to target them wherever they went, and set up infrastructure wherever terrorists were believed to be.

In my opinion, the only reason these military operations were possible is because neither had nuclear weapons. We were told Saddam had weapons of mass destruction, biological "dirty" bombs and such. In order to prevent him from building a launcher capable enough to hit America, it was imperative we invade and dismantle his regime. The power vacuum left arguably led to the rise of ISIS.

The AUMF allowed the military to target Bin Laden. The US had Intel that he was around Afghanistan, so they installed smaller outposts and attempted to find him. In the process, an arguably puppet government was set and trained by the US military to support democracy. For a while, people had more Western-style lives. When we pulled out, well.. Rights weren't quite as important as food. Current regimes are more like tribal warlords. That's more akin to how Afghanistan has been but it's rougher transitioning back under that type of Islamic rule.

When the military eventually killed Bin Laden, they were too embroiled with nation-building that all projections foresaw things returning to how they were. That was an untenable PR move for any president/party. The previous administration's decision to pull out, honored by the current, was done by design. It would have just been lost in another Trump news cycle if he won, and if he lost then he could bludgeon the Democrats/Biden with a botched procedure.

Afghanistan has trillions in mineral wealth, Iraq tons of oil. Trump suggested, on more than one occasion, that we jack it. The only way to do that is with a stable government/local military that could protect business interests. Given Afghanistan's landscape and history and people, that was almost certainly never going to happen.

Democracy was the long term goal. That would lead to better living conditions, and to a more stable government. Eventually, the US would reap the benefits by having almost a monopoly on the trade of those resources. Stopping Saddam and Osama were the short term goals. Weapons contractors were able to test, refine, and train personnel. Look at Russia's current military situation to see the benefits of that.