https://www.congress.gov/bill/116th-congress/house-bill/8356...
The original researchers still have their ideas and work, it was "just" copied. Still, we call it stealing and theft.
In this case, code was taken and the credit was stolen.
[0] https://github.com/spegel-org/spegel
[1] https://en.wikipedia.org/wiki/You_Wouldn%27t_Steal_a_Car
2 (transitive, of ideas, words, music, a look, credit, etc.) To appropriate without giving credit or acknowledgement.
When you download a movie from torrents, you don't submit it for an Oscar nomination claiming you've made it. You just copy a file to your computer intending to kill a few hours of your time while playing it back.
Microsoft®™, however, not only copied the code, but claimed it's theirs.
Claiming the code as authored by themselves did not leave the original author without their code. This would not be true had they stolen it.