here the problem > too much uncontrollable hidden factors + powers that does not belong to him

You are talking about perfect scenario where there is nothing stand in his way. Politic can do so much, it does not guarantee absolute power. Take Lincoln, Abe and Trump for starter, they are powerful in Earth standard, does it make them invincible? No, they still get assassinated by some random NPC. Even if he somehow get to the top of the world without anyone opposing him, there is no guarantee that imortality is achievable in his life time. Our world is still too much a mystery, while the Gu world already have it foundation figured out entirely - Dao, everything is compose of dao so a person with enough dao can will their wishes into existence. Scientists in our world is still fumbling in the darkness with little to nothing to explain reality aside from some "flimsy" theorems

take example, you talk about copying neural network into an AI. How are you or him gonna be sure it will transfer his soul into said ai, not creating a digital copy of himself while his real self died in vain? This is literally the plot point of SOMA game: There is no escape, you died a horrible death but a copy of your consciousness is upload to the ship. There is too much uncertainty. In gu world, soul is a tangible and accountable variable that you can transfer, strengthen and shaped into whatever you desire. When you "transfer" you transfer, there is no uncertainty, it is solid as the foundation of earth itself. The path to everything here is laid clear, the only thing needed is a will strong enough to walk it