All 3 are legit - it's a bit complex but here's the simplified version.
Olightworld is the factory in China.
Distribution rights in the USA have changed hands several times which is why you find these 2 companies; both of whom have held exclusive US distribution rights with Olight.
Currently Olight-USA has national (not exclusive) distribution rights and I believe OlightUSA also has national distribution rights currently (they changed hands early this year).
There are not '2 chinese companies making all of the various "brands"' but some are contract manufactured or have components manufactured in the same fabrication facilities and then are assembled/packaged/marketed by the manufacturer of record.
Employees have moved between the various companies quite a bit over the years and they're also hyper-competetive so when one of the more innovative companies comes out with something new you can be sure someone else will be following soon. Of course they all using the same LED's and a flashlight only really has a few major 'parts' (LED/reflector/switch(es)/battery tube/batteries) so most of the variation will be found in design details, fit/finish and UI.
Full disclosure:
I'm the President of Shore Power of which Olight-USA is a subsidiary.
I'm also an owner of BatteryJunction.com.
Olight asked me to jump in and clear this up.