they have been preparing, but you can't just develop an airforce or anti-aircraft defenses in the span of a year. this hige difference in capabilities was calculated.  what was miscalculated was the fact that israel would have knowledge on hezbollah's facilities to be able to hit them. iran was never going to go in, because that's what israel and the us want. it will be easier to defeat iran now than after 5 years. iran knows this and they don't take the bait, also because they are coordinating with russia and china.
Netherlands