Here's what I know from threads over the years...(as reliable as internet threads are)
Engineers from Pila left to form Wolf-Eyes.
Engineers from either Pila or W-E (forgot which one) left to form Microfire.
Don't know how Fenix started.
The designer of Huntlight FT-01 (Huntlight's first and most popular light) left and designed Lumapower M1. Some initial conflict ensued at the introduction of the LP M1, but it seemed to die away. Speculation: The M1 designer is probably still with LP and drives a lot of their development.
Don't know how Dereelight started, but initial design is similar to LP M1 (the way the module threads in, etc.).
Jetbeam was Emilions attempt to steal the 1AA market away from Fenix w/ the offering of a more premium 1AA light. MK1s were very well made and not too costly relative to the Fenix L1Ps at the time (I always thought the price of the L1P was too high for the performance. It has since dropped considerably and the performance of the successors L1S, L1T, and now L1D have continuously improved while pricing dropped relative to the L1P for what is offered).
These companies likely use the same, or same set, of contract mfrs in China. Often times, companies have agreements w/ more than one contract mfr (CM), which may explain some variations in quality and/or performance (one batch may come from CM1 while another from CM2, depending on company's demand relative to CM's ability to deliver). CMs often get components from distys (distributors) to more easily consolidate their supply chain, so everyone can get the same components, but since their designs differ, they end up using slightly different ones. Also, many CMs (both machining and electronic) have differing levels of quality standards w/ different cost for each level. To keep mfg cost low, the company may sign an agreement only forcing the CM to keep their design proprietary for so long (particularly the machining/mechanical design). This results in virtually identical copies a year or so down the road when the agreement is over. But, the copies may be mfr'd to a lower quality standard resulting in the differences in quality and performance you notice with the genuine vs. copy products.
The trend is that each of these companies is driving one another to provide higher quality products and better customer service as they notice which ones start to inch ahead of the others. This is good for us, but if this pace keeps going w/ new companies, the market may be flooded soon (like it already hasn't eh?) and my brain will just explode from too many options to review and decide from w/o enough time to look through everything.