Car slams into vehicle after being brake-checked on a busy motorway - so who is at fault?

A car accident which saw a ute slam into a 4WD has divided viewers over who is at fault. https://www.dailymail.co.uk/news/article-8927537/Car-slams-vehicle-brake-checked-busy-motorway-fault.html?ns_mchannel=rss&ns_campaign=1490&ito=1490