The phrase "surprise decision" refers to a choice or action that is unexpected and catches people off guard or causes them to feel surprised. Full definition
Though the biggest takeaway here is this: Whoever came up with this spent a lot of time thinking about how people think while shopping — and it led them to make surprising decisions. (entrepreneur.com)
Initially the A4 will be available with just the 1.4 - litre petrol motor which seems like a very surprising decision, considering rivals offer much larger petrol units. (carwale.com)
Hence his apparently surprising decision to retire from international football. (justarsenal.com)