Something is wrong with that commit count. There are a total of ~4k commits over nine years [1].

It looks like the author revived the project recently with the help of AI, but the majority of commits are from 2017-2024. Github might be counting all the branch activity from agents.

[1] https://github.com/Panzerschrek/U-00DC-Sprache/graphs/contri...

From the description of the graph you kindly provided:

  Contributions per week to master, line counts have been 
  omitted because commit count exceeds 10,000.