when the reformation happened why did those separating from RC church not go to orthdoxy, why did they invent new sects.
Disagreements happened throughout Church history. Many people seem to think that things like denying the real presence in the Eucharist came out of nowhere in the 16th century, or that the rejection of papal claims was absent in the west until the Protestant Reformation. They weren't absent, they were just sporadic and ignored, because the ideas couldn't gain traction and momentum. Eventually culture changed, values changed, governments changed, and an environment was created in which something like the Reformation could indeed take place. For a time people were still persecuted for their beliefs, people were still excommunicated, people were sometimes even put to death. But now there was sufficient backing, in at least some pockets of Europe, to make for more than one group wielding the club.
There was little contact with Orthodoxy, and what little contact there was probably wasn't very helpful. There were no ecumenical discussions, no attempts to see what was agreed upon. Whatever problems the Eastern Churches were having at this point (largely due to secular powers) they could all agree that they weren't going to accept various notions of that the Reformers would have put forward. And the Reformers weren't about to give up what they thought was right either. Such was always the way of things, but again, there simply wasn't a context to pull it off until then.
Well, but I suppose I am overstating things here, speaking as I was mostly of Europe. If we consider the bigger picture there were indeed times when groups split from one another, and those groups maintained their own identity, sometimes to the present day. Why was that though, why were they able to? Why were the Oriental Orthodox groups (plural) able to be separate in a sense from other groups (plural), yet maintain orthodoxy? Why were the other non-OO groups abel to maintain orthodoxy? The Oriental Orthodox (to focus on them a moment) could leave* because they were out of the reach of the groups we today call the Eastern Orthodox and Roman Catholics. Sure, the Copts, Armenians, etc. were influenced
by others (everyone is), but the thing is that they weren't secured in place, they were kept by force of arms or culture to stay put. And when they felt it right to move in a different direction, they did so. And yet they also maintained their orthodoxy.
So I guess, the thing is, humans like to disagree, so splits happen. Sometimes, despite breaks in communication, communion, or administration, orthodox values and beliefs and practices continue, though at other times they morph, or even are abandoned. Just part of life I guess.
*To clarify, by "leave" I do not mean to say "break off". Various groups essentially left each other, so far as I can tell. Or if someone left, it was not because of schismatic inclinations, but out of a sincere desire to do the godly thing.