The parallel between the two sentences doesn’t hold. In the first one, you give your opinion about Max’s gift. If you remove “trouver” and you just state a fact, you’ll say

Max a du talent.

In the second sentence, you give your opinion about the naturalness of Max success and not about the existence itself of the success. State a fact again, you’ll say

Il est normal qu’il ait du succès.
Qu’il ait du succès est normal.

But the use of the subjontif is quite complex and often a question of usage more than rational rules. See

Qu’il ait du succès est certain.
Il est certain qu’il a du succès.

Je trouve que + indicatif.

Je trouve __ (adj) que + subjonctif.

(expression figée)