If fracking in the UK is so safe, how did this happen?

Fracking has been used for well stimulation since WW2. The first fracking was carried out in the UK in the early 80s and has been used on over 200 fields, both onshore and offshore, including Europe's largest onshore oil field, Wytch Farm near Poole in Dorset. For 30 years no-one said anything until Cuadrilla declared they were going to frack in Lancashire. A reading of 2.5 on the Richter Scale is just on the edge of what might be felt by the general population - not quite as much as a bus passing by your window. The UK experiences thousands of these small tremors every year but only the British Geological Society are able to record them on their sensitive equipment.
I don't do any work for the fracking industry (and I have my reservations regarding the amount of water required to hydraulically frack) but I've sat in numerous seminars and between kips am happy with the safety of the practice - particularly given all the historical evidence we have. Correlation does not imply cause.

I grew up in Poole in the 80’s and 90’s and never felt a hung from Wytch Farm. Tbh it was so well hidden you only knew it was there if you wondered round to one of the far corners of Brownsea Island to look at it.

Here's all the human induced seismic events in the last 50 days:

earthquakes.bgs.ac.uk/induced/recent_uk_events.html

The last one, in Boulby, is the potash mine. It's a huge mine with wide roadways that stretch out under the sea from North Yorkshire. They have Land Rovers running around down there and when they come to end of life they don't bother bringing them to the surface, they simply drive them up a branch where mining has finished and wait for one of these collapses to flatten it like a tin can.

I went down there as part of a VI Form science trip.  It was MK3 Transits at that time.  IIRC the average life of a vehicle was 9 months.

I think that a problem with journalists is that they often fail to understand logarithmic scales, assuming that 2.9 is (say) half as bad as 5.8.  From what I can see, a difference of 2.9 represents a difference in energy released of a factor of roughly 31,500.