Because they can. Because they think it's fun, a challenge. I does not matter if only 10 people will use the result, it's all developed by volunteers. It has nothing to do with financial profits.Insert Ryan Reynolds 'But Why' meme.
If you can only get the M1 in an Apple product, isn't the audience for this work extremely limited? Apologies if I'm missing something fundamental, the number of people who will pay for an M1-powered Apple device and then Nuke the O/S seems vanishingly small to me - can someone enlighten me?