the earliest player ive seen doing anything like a euro step is bernard king on fastbreaks. he did that weave in and weave out move but it wasnt as exaggerated as it is today. i think players play lower to the ground today like they sqaut down closer to the floor and bend their knees way more. if you look at players like elgin baylor the main thing that stands out to me: they all stood straight up like a stick.
players in this era like iverson,wade,parker.... notice how hey all bend their knees in a almost semi crouch. thats why the eruo step today can be used effectively but not back in the day because back then all these players stood straight up at all times
just for a thought experiment try to imagine elgin baylor doing a iverson crossover while stnding straight up in his regular stance that he has. he probably would fall over.
Baylor does the Eurostep at 2:52
And at your second observation I do have a bit of context to help explain it - carry calls slowly but surely disappeared from his time to Iversons time - and this has effected the posture of players and how much they even attempted to dribble in the first place. Baylor dribbles palms down, so does all his contemporaries. It's harder to dribble this way because your potential "handle" is now gone - and as a result it changes your whole approach to what you can or cannot do while in a dribble. They all dribble far less often and keep their heads up because they all are occupied lookin to get rid of the ball right away to score or pass not keep dribbling.
Put your mind in their mind and you'll find that players today do two things vs players from Baylors era that would make them old dudes cringe like how u cringe when u see them standin up like a stiff - In our generation players *dribble too much, and *They commit carrying violations that never get called. (Iverson style crossovers involve cradling the side of the ball...)
A crossover ain't even somethin that those guys never knew about back then, a version of it existed and was used by Oscar Robertson and some of the smaller point guards who are less well known today but the move wasn't as impactful as AI's or Penny's cause they were doin it before the NBA was popular and it wasn't quite as fluid due to that palms-down rule. As time passed the NBA loosened its grip on how tight to call ball handling rules and ignoring things like carrying allow much more fluidity and style to the game which is the direction the NBA has been going since the 60's. Enabling simple things like that changes the dynamic of the game. So with all that said players went from standing tall looking for open teammates to pass too to hunkering down in iso looking to shake the D with tight moves and counter moves enabled by their added dimension of control