It was never a start-up, that was a complete lie that looked good as part of their marketing strategy to enter the US market. It's a bit deeper than Toyota since all of those smartphone brands belong to this company:
BBK Electronics - Wikipedia
If their brands were all counted as one, they would be the largest smartphone maker by volume of phones sold in the world. And frankly, they definitely should be counted that way.
Lexus models would largely be different cars, that brand was meant to be reserved for distinct, higher end cars made by Toyota. The brand has had its purpose.
What BBK Electronic does is, they design one phone, make three variants of it with minor modifications, and literally release it under three different brands. It sounds like the stupidest strategy ever, but it works, in particular in the US where people are happy to buy OnePlus phones but would never buy an Oppo or Vivo, even though it's the exact same "Chinese" phone - perhaps with a slightly smaller screen, or a slightly different layout of the same cameras on the back, made within the same company.
The structure looks like this: 100% of OnePlus is owned by Oppo, which is 100% owned by BBK Electronics. BBK Electronics is funded by the CCP and largely managed by members of the CCP that work for the company, as it is stipulated by the Chinese law. As a matter of fact, OnePlus is also required to have a CCP board within its ranks due to being headquartered in China and managing more than 10 engineers (that's literally the law in China).
Suddenly nobody is worried about Chinese dangers there, despite it being even more suspicious as the entire design and manufacturing is done in house in China.
In comparison, Huawei for instance is purely a multinational conglomerate. While the headquarters is tied with the CCP, they have many engineering offices in western countries. They are largely bound by international regulations and best practices when designing their software, for instance, a lot of which is developed in Europe.
BBK Electronics does everything in-house supervised by nobody but the Chinese govt, then they have to pass bare minimum regulations (such as emissions, bluetooth certifications etc.) and they're good to go to be sold abroad. Huawei had their own US offices offering local support, marketing and dealing with regulatory bodies locally in the US. With OnePlus you are dealing directly with China, with a tiny team consisting of a few people hired in the US, England and India facilitating that communication. People are incredibly chill about OnePlus in the US compared to the mainstream hate bandwagon companies.
