For comparison, the transition from PPC to Intel started in 2006 and the first MacOS version to require an Intel processor was just 3 years later in 2009[1]. By comparison, the M series transition started in late 2020/early 2021. That said they were still selling Intel based macs up to 2023, but if you were buying an Intel Mac Pro in 2023 you had to know you were buying dead end tech.
[1]: https://en.wikipedia.org/wiki/Mac_transition_to_Intel_proces...