The goal is to sell weapons during the war; then afterwards, sell loans to rebuild what the weapons have destroyed... And sometimes it's also to control access to natural resources or trading routes. They don't care who it is who facilitates them on the other side of the ocean; be it a dictator or an 'elected' official.
The lobbyists running the show in the background make money from both the destruction as well as the reconstruction. What is stupid about that?
The politicians later get appointed to lucrative executive roles at the companies which they helped enrich on taxpayer dollars (from both countries). Not stupid either. It's smart retirement planning.
The government is a lot of things but absolutely not stupid; fooling people into thinking it is incompetence is likely part of the ruse... It's a lot easier for people to sit back quietly and watch incompetence unfold, then it is to sit back and watch evil unfold. "It's incompetence" is also a nice easy answer which prevents people from having to look deeper as I have done here.
Julian Assange said about the war in Afghanistan: "The goal is to use Afghanistan to wash money out of the tax bases of the US and Europe through Afghanistan and back into the hands of a transnational security elite. The goal is an endless war, not a successful war."
If you look at any war, you will realize that the same principles are at play. Our current global monetary order has a built-in mechanism for monetizing destruction, unfortunately. It's architected that way, intentionally or not.
I've dedicated much of my life so far to try to convey this simple message.