if you start critically analyze AU scenarios, everyone will in the end prove out to be impossible if compared to real life.
Again, Golly, you're far off the point, I'm afraid. I have been engaged with AUs since the 1990s in a "manual" form (i.e. no computer simulations etc), and was a longstanding member of Panhistoria when it flourished in the early 2000s. (I went dormant around 2005, due to other, more important commitments). I reiterate that well-thought-out AUs, CAN
be possible and plausible - even compared to real life.
Think of this: what if the 12" shell from VADM Togo's flagship Mikasa
had not hit the Russian fleet-flagship Tsesarevich's
bridge during the Battle of the Yellow sea, Aug, 10, 1904, killing VADM Vitgeft, his chief-of-staff, RADM Matushevsky and, most importantly for the subsequent events, the ship's helmsman. I'm not going into detail here about what this hit resulted in, since there's ample literature and webpages that can be accessed about that. Point is this: an event that was slowly, but, what appeared, inevitably unfolding: the Russian squadron actually pressing the Japanese battle squadron away, opening the path towards Vladivostok, was ultimately changed by that freak Japanese "lucky" shot.
One, seemingly small event or incident, that had enormous consequences! Such are the tweaks I'm referring to.
I'm not particularly fond of adding new landmasses hither and tither, I just don't believe in that, but there are a few well considered AUs here, that make use of existing conditions, but, again, tweaking history's progression, just so much as to enable their AU. Certainly not impossible if compared to real life; however you analyse it.
But, it goes without saying, that such successful AUs behind them have a solid foundation of research. - And that, Ladies and Gentlemen, is the BIG
secret, to enable the possibilities inherent in an AU scenario.