Of course his foot is off the ground. He's stepping sideways.
This is the farcical nature of the argument for it being a red. The logical conclusion is that simply running with the ball, if you're unfortunate enough to have an opponent slide in and get their leg under your foot, is now a red card worthy offense.
Football is a contact sport and sometimes that results in weird injuries from otherwise innocuous things. This was one of them.
Rashford fairly shielded the ball from a player trying to tackle him, but the outcome (which ultimately wasn't even that bad) has led to hysteria about endangering opponents with run of the mill football techniques.
The action is what should be punishable. Not the freak outcome.
There's a difference between stepping sideways and stepping over a ball though, anyone who has played a football, which I assume includes you, knows this. The force of stepping over a ball includes your body weight moving across onto that side as the whole point is to then shield the ball when your foot plants onto the turf. If that foot reaches the opponent before the turf they get a lot of that energy coming across. Rashford isn't a dirty player, none of it was meant, but that is factually what happened.
In my mind your scenario is easy to put to bed. Player A in possession runs down the wing, opponent player B attempts to tackle him, misses the ball and player A stands on his leg whilst running leaving player B shouting in agony and demanding a red card for player A. In this scenario, player B has made a fair attempt to play the ball but is not successful, player A has done nothing but continue their run. In the same way Rashford makes a fair attempt to shield the ball but the action is not successful. If he'd got his foot to the ground (action complete) and then the player had run into him and gone down, he's getting jack shit.
I'm not sure there's a huge amount of hysteria, just the thought that studs into the ankle is fecking painful and can cause injury.
Bolded part doesn't really make sense. It's basically one of two outcomes.