Why did Clinton give china nuclear submarine technology?

Communist China already had that technology. Refined and advanced technologies are always being swapped, stolen, or bribed by the covert/espionage people. For example, the USSR (today called Russia) received their first successful 4 engined bomber from the US; they stole it when one of the US B-29s landed in Russia from a bombing raid over Japan in WWII. Instead of returning it, they dissembled it bolt by bolt, and copied it bolt by bolt (under Stalin's orders), then they had their brand new B-29 Russian (Soviet) version. Same with the atom bomb; a US couple (husband and wife) sold/gave the US A-Bomb secrets to the Soviets (Russians) and the Soviets successfully exploded their first nuclear device in 1949. The couple that gave the secrets to the Soviets were executed in the US on or about 1955.

The first US tanks were copies of the British MK series and the French Renault model 1917. The very first German tank was a captured British tank, repainted with German markings and sent back across the lines to attack their original owners.

The US 1903 Springfield bolt action rifle that was supposedly all US designed and made had to pay Mauser for patent infringement fines.

The US Civil War Confederate iron-clad, the CSA Merrimac (or CSA Virginia) was a rebuilt CAPTURED US (Union) vessel.