The answer to that would be to not desperately stretch your leg and studs out.
He doesn't. Watch it again, his toe is pointed to nick the ball until it connects with Bellerin's leg and his weight follows through. He was leading with his toe rather than his heel before that point.
That's the reason that most of these challenges are red cards because they have the potential to be career ending, whether you intend it or not.
As I said above, it's not one of those challenges he's leading toe first.
You can't do something desparate and then ask what you were meant to do after it. I seriously doubt that in the same fraction of a second that you're giving Pogba to react to what happened, Bellerin had time to run through his head how he should position his body, or even think about his leg let alone think about folding it in such a way that his calf did anything.
Bellerin's action was proactive, he was standing his ground with Pogba motoring towards him and knew all Pogba needed to do was touch it around him and he was in trouble so he made the decision to focus on obstructing Pogba's path rather than the ball. Pogba was moving towards the wing and Bellerin was on the inside of him so he moved wide to block him and the best he could do to challenge for the ball was wave a leg at it which is why despite being in good shape and balance to make a normal tackle he ended up in a weird position with only his leg making any connection.
You can't absolve Pogba of doing anything because he only had half a second to react but then blame Bellerin for something that he'd need 10 seconds to plan through in his head in a fraction of a second. That's a little disingenuous.
Look at the caps below and bare in mind this is slowed down x3. Bellerin throws himself past the path of the ball and into Pogba's Path. He made that decision with far more time to think about it than Pogba.
Pogba could only realise where Bellerin was going to land by 2.31 and he connected at 2.93. In real time that would have given him about 0.2 of a second to react and change his whole momentum.
The last caps show he was leading with his toe and connected with Bellerin toe first before his body weight followed and forced the rest of his boot to land. Avoiding a collision after Bellerin moved to body check him would have been impossible and why shouldn't he try to toe the ball when a player is trying to check his path?