Alex had previously nominated Elena and Jason for eviction with Cody Nickson as her backdoor target. The only reason Matt was on the chopping block was because he intentionally finished the "Temptation Competition" in last place, so he's the week's special third nominee.
Matt's objective in throwing the competition was to stop Cody from a last-place finish since it would guarantee Cody a nomination and therefore a spot in the Power of Veto competition, meaning he would be able to compete to save himself from the chopping block.
Alex originally wanted to nominate Elena and her showmance partner Mark, but Mark had received immunity for winning the "Temptation Competition."
Since Cody was not picked to play in the Power of Veto competition, Alex's plan to backdoor him was being executed perfectly.
Big Brother's PoV competition was a classic in which the players participated in a prize-swap challenge. Every time a player was eliminated, he or she would pick a prize. Just like in a Yankee Swap, that houseguest can then choose to keep the prize for him or herself, or trade it with a previously-eliminated contestant.
The live feeds say Elena stole $5,000 from Alex, who then got stuck with a curse in which she must cook hot dogs for her fellow houseguests at a campsite every time she'd prompted to do so.
While Mark won a trip to Colorado, Jason got stuck wearing a giant X helmet and matching costume. In a similar punishment, Paul and Christmas Abbott were forced to dress as tandem skydivers attached to one another. Paul and Christmas must also get around the house on a scooter together for the week.
In the end, Matt won the Power of Veto. However, if he chose to use the veto to take himself off the chopping block, there would be no replacement nominee, meaning Cody could not be nominated for eviction in his place.
As a result, Matt was pressured to take one for the team in light of Cody trying to work something out with the houseguests and Alex being angry with Elena for taking her prize money away from her.
At the Veto Meeting, Matt decided to use the Power of Veto on Jason, allowing Alex to name Cody the replacement nominee. The final three nominations will therefore be Cody, Matt and Elena going into this week's live eviction episode, with Cody being the house's target.