Yes, multi-player Ambassador is very weird indeed. In this particular game, there were no other cursers. As expected, the estates pile did empty. There was also another cheap pile. Squire, I think? I opened Transmogrify/Ambassador, showed my trick which started a curse war and ultimately emptied the curse pile, and as everyone struggled to figure out a way to buy a Duchy or two with no trashing in the kingdom(!), I three-piled the Squire, having given away no Estates at all, and won on the strength of all those 1-pointers. It was a very strange, don't-try-this-at-home kind of win (7 points!)
I remember one other oddball Ambassador game where I got caught flat-footed. Again, multiplayer, and again, the inevitable rush to empty the Estate pile happened, at which point my wife, who had not even purchased an ambassador(!) had been sucking up the estates and maneuvering to try to exactly hit 7 with silver and a little bit of draw. Then she Inherited Crossroads. With a deck consisting of over 20 estates. I've never seen anything like the next few turns: Crossroads draw 2, Crossroads draw 5, Crossroads draw 8, buy a Province. I suppose I should have seen it coming.
I'm pretty good at two-player, but multi-player can be so unpredictable. How many people are going to go for Fools Gold? Enough to make it worthless? Will enough other players use that attack card with a marginal benefit against each other so that I can just sit back and defend and advance my position without having to buy any of them and pollute my deck? Which possible deck archetypes have the same couple of opening buys so that I can switch strategies after seeing how my opponents open? Will a pile empty fast enough to upgrade Cities? Will getting to a Province a turn as quickly as possible win a race, or will player B be so slow in getting his share that player C will have time to set up a couple of double-buys to pass me? I can see why it's so hard to simulate.