The Explorer is unsafe, because if it does roll, it will be crushed by its own weight, regardless of speed. 1 in 2,700 Explorers manufactured between 1990 and 2001, has been involved in a fatal rollover. The numbers are worse for its predecessor, the Bronco II, where it is 1 in 500.
I couldn't find a source of truth for Cole's speed at the time, but by all accounts, it didn't sound like he did anything else wrong (he swerved to avoid a car driving on the wrong side of the road).
Coles swerved to avoid a driver heading toward him in his lane, and the Explorer rolled over. Coles ejected from car, tho he wore seatbelt.
2. 80 (mph?) is not that fast, less than 130km/h
[Edit: There's three issues at play with the Ford-Firestone debacle; The Explorer was poorly designed and prone to rolling (moreso than other SUVs), The Firestone tyres fitted had a habit of delaminating, which caused a number of rollovers (but that wasn't the cause here) and finally, the roof pillars weren't even strong enough to support the weight of the car, so when it did roll, the roof crushed in on the occupants]
Brief readable summary: http://www.the-injury-lawyer-directory.com/negligence.html