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>>51030929 says, shitty writing.
He had the potential to be a good character just as SwSh plot could have great, it had all the basic elements to fit very well in the overarching themes of human progress vs the natural world found in all pokemon games.
Instead, Gamefreak being Gamefreak, they made him look like an autistic magnate that turns villanous because he wants to solve an energy crisis that doesn't exist yet, with a risky plan that involves summoning a destructive supernatural entity. Which is fucking stupid and doesn't make sense, and makes his redemption in the post game feel unjustified.
A decently written plot would had either made him:
A) an actual intelligent and well intentioned person that realizes Galar is facing an IMMINENT energy crisis that will make the region poorer and worse to live in. Not seeing any other way to solve it, he resolves to summon and control Eternatus, being aware this will make him a villain in the eyes of the protagonist. This would partly justify his actions and make his redemption feel deserved.
B) a greedy scumbag that simply wants more power for himself and his own company, he makes up the crisis and uses it as an excuse to rope Leon and other trainers in his service. Nothing wrong with irredemable villains that are in just for money and power, fits right in with Giovanni and Ghetsis.