Not being loyal/reliable is unimportant to the US in this matter. I (US) just want information, it’s strictly transactional. The reliability can be cross-referenced.
No, loyalty does matter, even if its motivated purely by money. The US doesn't operate like in your spy novels. They don't just want to buy info, they want to buy control. Control allows them to do things, like Ukraine.
Ideology is pretty much irrelevant. Why does someone in Malaysia care about helping China? HK and even Singapore are different, one is actually a part of China, and the other is a Chinese ethnic-majority country.
Any other explanation besides “new Mercedes” is overthinking it.
Again, you over-simplify. "New Mercedes" is only for the a few people in high places. You can't be handing out "new Mercedes" to everyone to buy their loyalty. Why is ideology relevant? Because that's how you organize the masses to do what you want. That's how you make things happen. How do you get the average idiot to hate the Chinese? Through indoctrination via the media, education system, and religion. Do it long enough, and the ideology far outlasts any money you've spent on bribing.
Why does someone in Malaysia care about helping China? Why alot of the Malaysian Chinese do care! What motivates them? Money? Yeah. Chinese identity ideology? Even better! Because of ideology, affluent Malaysian Chinese made donations to China when it was poor. They even make donations to their ancestral villages in China today. Because of ideology, many Malaysian Chinese organized medical donations to China when Covid-19 first broke out in Wuhan. What "new Mercedes's" were needed for that? Concluding that every explanation is all about money is ignorant, and quite frankly, disrespectful.