So...he checks right, sees Alonso is not there, and then decides to break the tow to the left?
"he checks right, sees Alonso is not there, next he checks left, sees Alonso is not there either, and then decides to break the tow to the left", is what happened. You'll have to ask him why he veered left rather than right, with both options still being open (*), but if I were to take a guess, it is because not even Stroll would open up the inside line, and also because he would have to check his right again if he were to go there.
(*) Excluding the fact ALO was already way too close to even consider breaking the tow, or basically doing anything else other than squeezing his buttocks while hoping ALO isn't actually way too close already.
Stroll himself said that he moved late. Is that not basically admitting it was reactive?
"He's clumsy all right". He let ALO get too close prior to attempting to break the tow.
But it's ok. I'll happily sign off on STR being superhuman (reacts within a 10th of a sec) and evil (surely knew he'd send ALO flying). I mean that's what you're all saying right?