OK, so Transformers as a brand is a collaboration between two toy companies - TakaraTomy in Japan and Hasbro in the US. Most of the original Tranfsormers were originally Japanese toys released by Takara (as they were then) in two toylines - Microchange and Diaclone. When Hasbro were shopping around for toys to import to the US, they licensed both these lines from Takara, as well as a few other toys from other manafacturers (most notably Takatoku's Dorvack, Beetras and Macross lines).
In order to sell the line in the west, Hasbro hired Marvel to come up with a backplot, characters for the toys, and the comic and cartoon, predicating the smash hit Transformers would become. A year later, Takara would cancel Microchange and Diaclone in favour of launching Transformers in Japan, translating the cartoon and making their own comics based on the line. The proposed 1985/86 Diaclone toys were shifted straight over to Transformers for both Japanese and Western releases
Since then, Takara/TakaraTomy and Hasbro have been pretty close in terms of working together on toylines, though the creative drive has shifted back and forth over the years. Between 1987 and 1992 Japan did their own thing, spawning 3 50 (or so) episode TV series, direct to video animation, comics, and a whole mess of toys that never came out over here, and many of the ones that did had different paint schemes and characters.