Where did all the goblins go?

[Kuruharan]

Yeah, exactly like what happened after the War of Wrath, and they survived then (Sauron was not present at that time! And they were bound by the will of Morgoth, not Sauron, and as you can see, there was no problem).

There is some question presented in the books about whether his repentance was genuine. In any case, there was still a great force of primordial evil present in the world capable of chaining the wills of the orcs.

It may also have something to do with the fact that Sauron was the one who created the orcs in the first place.

Or after the war of the Last Alliance, and they survived again.

The Ring still existed. Sauron still existed. What is your point here?

But Orcs? They were "normal" free-willed (now really) beings. The Power that ruled them was gone, yes. Their leader and shiny future (for the carieristic or fanatically devoted Uruk-hai) was gone. What a shock for them.

There is a lot to question about what exactly the orcs were and whether the bulk of them were "rational." It is ultimately an unanswerable question because Tolkien changed his own mind on the subject a number of times.

Here is a cursory treatment.

If you really want to get into some nitty gritty (and delve into the bowels of the site, waaaaay back into its earliest days) click here