Probably believed his own delusions and those of his sycophants. Now they're in the find out phase.

Seems like Israel pushed for it. The Trump admin was clearly trying to back down without admitting defeat before the Netanyahu meeting a couple weeks back. The smart thing to do now would be to back off now and let Israel take the fall.

He wanted a quick decisive strike that would force Iran to capitulate to his demands. He probably thought things would go the same way they did in Venezuela.

like 90% chance he has dementia who knows what has been whispered in his ear

When you fill your space with constant praise and people telling you only what you want to hear, this is the result. Generals were afraid to tell Lyndon Johnson how badly things were going in Vietnam, and kept feeding him false reports of thousand of NV and Viet Cong losses. Johnson was gobsmacked by the "impossible" Tet Offensive, which may have led to his decision not to run for another term.