Why did Liz Truss change her mind on Brexit?

Rishi Sunak and Penny Mordaunt were both committed Brexiters in the 2016 referendum campaign – and both took career risks to support leaving the EU, against the wishes of the then-Prime Minister David Cameron. By contrast Liz Truss campaigned enthusiastically to stay in the EU (see for example the below forceful speech to the 2016 Food and Drink Industry dinner where she makes a powerful industrial case for staying in the EU).