This paper argues that electronic locks played a large role: https://link.springer.com/article/10.1057/s41284-024-00452-2

I would bet that the pervasive use of electronic records has something to do with it, too. According to this 1979 report from the Nat'l Assoc. of Attorneys General, in the 70s there were a lot of paths to retitling a stolen vehicle back then, which along with the the rise of chop shops and easier export of stolen cars, supported a large stolen-car economy: https://www.ojp.gov/pdffiles1/Digitization/59904NCJRS.pdf