Thousands of scientists, and hundreds of tons of documents. Industry and business also hoovered up all kinds of proprietary techniques and processes as part of what was termed “intellectual reparations” or somesuch.
Less well known, Paperclip also imported a lot of chemical and biological warfare scientists, and propaganda specialists, and other super skeevy types. By the early 1950s the spook agencies were doing all sorts of crazy stuff with mind control through hypnosis, hallucinogenic drugs like LSD and BZ, assassinations. MKultra is probably (now) the best well known.
The government imported both hard core Communists and Nazis to the USA and installed them in high places.
What could go wrong?
Indeed.