As others have said, money is most of it.

But I also remember that what seems to have prompted his last few years of total unhinged behaviour was his daughter turning her back on him. That seemed to be the point of no return for him.

So there is part of me that thinks he wants to have access to and control over data. The whole nazi salute wasn't about money, it was about ideology and I think controlling data will allow him to go after communities of people as part his ideology.

I'll give you a hint. It starts with an "e" and ends with "mbezzlement"

His entire plan is to cut as much as he can and funnel it back to himself and his billionaire friends. He's not looking to cut waste, he's looking to redirect it.

Classic billionaire were pushing for low tax, and low gouvernement spending, so they don't give their money to the government. Musk is more the banana republic type billionaire, who is in favour of high taxes and government spending going in his pocket. As easy as it

He doesn't know either. People give these fuckers far too much credit. He doesn't have any sort of big strategic vision. He just acts out his base impulses and does whatever will feed his narcissism the most at any given moment.

Compensating.

"I'm the richest man in the world, I must be the best. Why don't people like me? I'll make them pay for mocking me..."

He's being a Nazi

Revenge plays a part in it. But more importantly it's narcissistic ego trip. He needs to prove to the world he's the best, the smartest, the only one worthy to be a savior.
Being humble and making small changes will not result in Musk being celebrated as the most important person in history, which is what he really wants to be. If it all fails it doesn't matter, because somebody else being celebrated as having the right idea is an even bigger failure for him.

doing all he can to gain more power and get more ways to crush opposition. He has already subverted democratic process. When did he get elected to do stuff that affects your government and country?

All of this is so that after they have made it nearly impossible to be investigated, held responsible, or audited, they will run a big expensive scam on the government dime and cash out. They are bank robbers. This is the plot to Die Hard! The only difference is instead of stealing treasury bonds from an exchange, they plan to issue the bonds to themselves from the treasury building!

Follow his Masters' demands.

Destabilising regions and install pro-tesla/anti-regulation government, doing whatever the latestage capitalism is doing. The billionaires lining up behind him like a dog is the proof.

Acting like if he owns a country and its institutions?
I do wonder for how much longer Trump will tolerate such a diva standing right next to him on scene?

(that's coming from a non-US citizen. I may not be the most well informed, mind you)