I think it's a different reason. Let's analyze the outcomes from game theory perspective, along two dimensions: virus becomes pandemic or not, and governments do something or nothing. 1) no pandemic, no action -> government was "right", avoided wasting money -> reelected 2) no pandemic, action -> government was "wrong", wasted a lot of money, damaged the economy, inconvenienced the lives of the population -> voted ou…
That's now how game theory works, the pandemic is not another player who is 2nd guessing the government or vice versa. Instead governments are weighing the probabilities (think a probability tree, according to your scenarios) you kind of point to this in your conclusion.
The 2 players here are the government, and the voters. The socially optimal scenario is action REGARDLESS of whether it's a pandemic or not (in a hyper-globalized world it would hurt a bit, but only the first time, after that the tourists, supply chains, etc. would adapt) but the voters penalize that outcome (they see action with no pandemic as overreaction not as successful prevention) so governments avoid it.