My 2 cents
The faliling oil price is a negative symptom of weak demand and over supply of oil. Many oil economies need an oil lrice of $60-70 to break even, as price fell below that they kept producing. Even Saudi whonporduce at 10 need a lriceof 60 (I recall) to meet govt spending based on their production volume. Now storage is full. Weak demand esp from China is a worrying sign that their economy could collapse, they are a big consumer now not just a producer. Spending on oil production and exploration is being cut back so that less jobs, tax revenues etc
As such investors are taking money off the table / out of the market – in fact they’ve been doing this for months
Being prepared for such a scenario was one of the major reasons the Tories favoured spending cuts to more government debt