Why was it a foul by the goalkeeper on Jota? You haven't even considered that it could have been a foul by Jota on the goalkeeper, and you have even said in your argument that Jota moved into the 'keeper.
Goalkeepers always have a lower center of gravity when challenging, because they are positioning themselves to be bigger, wider, and consequently lower to the ground. Any collision is likely to result in the attacker falling. Add some theatrics to the equation, such as the throwing of hands into the air, and the penalty question arises.
It was the same with Ederson v Odegard recently. Odegard stood on Ederson then went down, but there was still outcry for the penalty, at the time and ever since.