Without control over your technology, you will literally die immediately of an invasion. Besides, it's easier to import food than nuclear bombs.

If we are talking about End of the World level conflict, then yeah no preparation would mean anything, but that's not the case for most of the conflicts, if any since WWII, aren't they?

And TBH, following that reasoning, that there is nuclear bomb, ground force should be cut to save cost and tax money too.

Yes, if you are a country that only wants to protect their homeland, cutting your ground forces as a result of nuclear bombs and ICBMs is perfectly rational.

Say that you are a citizen of a country endlessly threatened by invasion from a foreign power. Is it more important for you that your country has the nuclear bomb, which means your likelihood of being turned into glass falls from 50% to 0.1%, or that your country has greater control of agricultural production, meaning that in case of disaster you won't have to pay fortunes for imported food and cut your consumption? I'd say in this case the nuclear bomb is more important.

Also, we didn't see End of the World level nuclear destruction of any country because all the great world power developed the Nuke. The US Army very seriously considered using nukes in the Korean War as well as had plans for the invasion of the USSR (See : Operation Unthinkable and Operation Dropshot). The only reason these plans weren't carried out is because the USSR and China sacrificed very heavily in order to develop their technology and achieve technological parity with the West.

Tell that to the Lebanese. After the Beirut explosion took out the nation's largest grain depot (half of it got blasted to shreds by the explosion, the other half was contaminated) and the entire infrastructure of their dominant port, they're squarely fucked.

If a country loses access to state of the art tech, they might as well become a third world country within 5-10 years.