Can you explain the logic behind putting Kumawakamaru so low on the list, and buying dora/mimzee before atman?

It doesnt make any sense to me. Early game, your goal should be to get to higher levels as quickly as possible. Kumawakamaru decreases the amount of time it takes to get from 1-100 by over 50% (some people say you miss out on gold, however the gold you miss out on is negligible, as we all know the best level for farming gold is the highest possible level and getting to higher levels faster means you level faster etc etc etc, the arguments are other places on this subreddit)

however, kuma only costs 140 HS to max. thats 140 HS(+buy cost) to decrease your time from getting from 1 - 100 by over 50%. It seems like this is far more cost and time efficient than investing in dora + mimzee this early because you can max it relatively quickly and its cheap. very affordable for new players and if you are focusing on multiple quick ascensions to accumulate hero souls quickly, you want to get to high levels faster because it means you acquire the gold

dora, on the other hand, costs about 1400~ HS to max which is roughly the same as atman,

however, buying dora commits you to mimzee, another relatively expensive ancient, and atman on the other hand increases your primal spawn chance for the same cost as dora.

Even if you are only making 6 HS between 100-140 (not including hero levels), atman would increase that to 12 for the same cost as dora, and the quick ascensions due to the 140HS Kuma means you reach a quicker progression much faster because of how cheap it is.

can someone actually show me math that makes a case for buying dora/mimzee before kuma in an idle build?

I mean this build has it at #9. I feel like in terms of both cost and time efficiency, its far better than that.