It's a trick riot keeps secret : if you bought a couple skins, they will give you good teams. If you don't pay, they'll make sure you never go past silver elo.
They know perfectly how to screw a game : you won't realise it at first, you'll think you're just unlucky because you got inters 3 games in a row. "it must be my fault, how can I carry this?"
but in fact they set up teams so that you will most surely lose : they just need to place you with 2 uncarryable burdens. With 2 inters in his team, even a challenger will lose : https://www.youtube.com/watch?v=NP7_ts3j594
It's a trick to give paying customers a feeling of satisfaction.
Then when you tank very low, they'll give you a couple wins to keep you afloat and see if you give money. If you don't, they'll make you lose again.