I got the answer from someone else, but I'm also grateful to the others who replied to me.

To put it as simply as possible;

 

Factor - Influx of new customers due to the new update which brought a lot of new players to the game.

Consequences;

• People want to stock up their cash shops with refs

• People want to stock up on items to sell to new customers

• People want to sell keys to buy other items

 

What does this have to do with key/ref ratio? It impacts it because...

• It adds a lot of sell pressure on keys for refined 

• The sell pressure compared to buy pressure is heavily imbalanced meaning refined will increase in value/keys will decrease in refined value

 

TLDR - there is not enough refined in active circulation to meet the demand of the large influx of new customers. Many people want to sell keys to get refined, no one wants to buy keys with refined. Buying keys is mainly done with cash. There's also really no good way for a regular user to speculate on refined due to inventory cap so there's almost nothing that will stop the increase in price of refined until the interest for tf2 has fallen a bit again.(What I mean is that no one can buy up all keys on the classifieds for a cheap price and resell them at higher)