Usage of に with 分かる in this context? Why isn't が used?

Question

The context is essentially a monologue where the MC comes to the conclusion he understands his friend's problems and the friend problem with his brother.

尊敬していた兄の失踪。自分は兄の悩みを一切を知らず、しかし共有していた。

そう理解した瞬間、天道の苦しみの一端がするすると心の中に入ってくる。

締め付けられるような喪失感、悲しみ、後悔、恐怖、そして寂しさ。

（共感とは、言葉にしてしまえば陳腐だ）

だから天道にわかりますよ、とは言わない。言ってどうなるものでもない。

"The brother he respected disappeared. He didn't know what kind of pain his brother was going thought, and yet he shared the same problem"

"The second I understand (his situation) I understand a part of 天道's struggles and they enter into my heart"

"A sense of loss, sadness, regret fear and finally sadness"

"If you put sympathy into words, it's cliche"

"That's why I won't say I understand 天道. Even if say, it won't make a difference"

As far I know, in 分かる the に denotes who is doing the understanding and the が what is being understood. The whole monologue is essentially from the protagonist coming to the conclusion he understands his friend 天道's problems.

From this context I can only gather he's saying "I won't say I understand 天道" but why is the に used?

Answer 1

This sentence is technically ambiguous:

天道にわかりますよ、とは言わない

1. I won't say "I understand [you/it]" to Tendo.
2. I won't say "Tendo can understand it".
   _{(cf. Use of に in 「私には本物の若殿様がわかります」)}

In this context, the first interpretation is correct. In other words, に connects not to 分かる but to 言う, and に simply marks the listener of the action of 言う.