The point is that with the stock market you need other people to also agree with your stance in order to profit, whereas when you book a vacation your only need is flights to keep departing and hotels/resturants to stay open and accepting guests, plus the avoidance of lockdowns at destination.
Plus the first rule of every game is to optimize for playing against weak players.
On the stock market and prediction markets one is playing against very strong players, information asymmetry plays a huge role and perhaps insider trading (especially in this case where technically any information on the pandemic outlook is not considered insider trading )
On TrivaGo, Expedia, Booking.com... instead the opposition is basically other would be vacationers , and that has to yield larger return