[DNF2]

This is just a disagreement over basic design: should variable declarations be explicit or not. It is a choice, and something that reasonable people can disagree on.

Framing this as a case of irrational and illogical behaviour is unnecessary and unreasonable in my opinion. A lot of serious thought and debate went into the resolution. There is no need to disrespect and badmouth people because they have different priorities than you.

[systems]

Can you tell me one design benefit (a real good one) for not declaring variables before their use, in a mutable by default programming language

[DNF2]

I don't have a strong opinion on this, one way or the other. It's less verbose (which I like), and more familiar to those used to dynamic languages like python, matlab, etc. But this isn't my decision, I'm ok with either.