These decisions are subjective. I think it's harsh to criticise for decisions that are 50/50.Dias got to the ball first was in full control the Leicester player jumped into Ruben should have been a foul for City
It doesn't really matter who got to the ball first. Dangerous play is just that, no matter who gets to the ball first. An overhead kick looks spectacular, but if a boot is flying past lots of heads, it is dangerous.
The law provides that if a challenge against an opponent is considered to be careless, a direct free kick should be awarded. Careless is when "a player shows a lack of attention or consideration when making a challenge or acts without precaution." Now personally, I don't think Dias was careless - his challenge was quite careful in the circumstances. I don't think this was the worst refereeing decision today though, and for a newbie, we can afford to cut the referee a little slack.