Any other explanations as to what's causing this BTC upsurge?
Everything in this market is speculative and none are concrete so if you are seeking for exact answers then you find nothing in return so better bear with the flow
Bitcoin starts to grow as I think bull ihas come from that date and in April the run started and we can see that on chart from April to July when we almost hit the $14k value in which pretty high since February of 2018 .
So for me its the investors who comes back from the rest since 2018 darkest moment of crypto