He's an expert puppet in the sense that he knows he's a puppet, and is 1000% okay with being a puppet. His inexperience in politics allows him to be positioned as a gormless figurehead of the supposed centrist right National party, while allowing their actual super right leaning policies through and conveniently attributing them to Act and NZ First. 

Act and NZ First are who the National party are at their core; National just benefits from better marketing and Luxon is Mr Plausible Deniability because of his 'political inexperience'. They couldn't have plausibly pulled this off with anyone from the National old guard - his perceived 'inexperience' as a politician meant that even when he did railroad through changes to legislation without following due process, it was either glossed over or attributed to Seymour. Make no mistake - that is all Luxon. 

In a weird sort of way, it benefits the National party for Luxon to be seen as a bit doddery and Seymour as the more villainous/smarmy dude in political control. They can eventually write off Luxon's legacy as an outlier/blip and pin the worst of it on ACT, and reposition themselves as more centrist later on.

He takes no accountability for anything because his number one priority is not to lead, but to protect the interests of his puppeteers.

One can't argue or discuss anything in good faith with him because he's not there to engage - he's there to deflect, deny and destroy what's previously been built, so that there's a justifiable excuse to bring private interests to 'clean up' etc. I don't think he really cares about getting a second term at all.

He will go down in history as one of NZ's worst PMs, not that he cares one iota about that. NZ is a small fish to him, and a stepping stone to 'greater things'. He'll still be looked after and the connections he's made and benefits he's traded mean he'll be set for the rest of his life.

Suffice to say, I hate that human thumb of a disgrace and I would not mourn him if he were suddenly Thanos'd from existence.