Because a Company like Tsingshan does deep DD before taking on partners and makes plans for years ahead.
Foxess probably needed a shiny suit, being a named U.S. partner, before filing to go public to look good for prospective investors.
nobody else raised their hand and didn't need Foxess unknown new brand since there were at least 30 different inverters already on the market being represented in U.S.
unfortunately they didn't realize they bought a cheap suit and already worn out with only 000000000's on the foxess scoreboard.