So the market isn't really irrational. You might argue our interest rates and monetary policies are irrational. I would agree with you.
It's also a bet that they will fail quick enough to make this the best opportunity for your money.
This doesn't happen until trades from the IPO "settle" t+2 (standard time for a trade from a buyer to a seller to be booked, and for a buyer to actually receive ownership of the shares. Ownership in this case meaning you can lend / margin them etc)
Options usually won't be listed for a week or so at the earlier until after the IPO, so whoever mentioned that below is wrong.
Varies deal to deal and if traditional listing / direct but that is the gist.
You cannot short post IPO until the stock becomes marginable.
What you can do, if have a lot of $$, is have one of the desks immediately at after the IPO write you a synthetic short position using an over the counter option.
Up, or down, there are always sales at hand in price movements. And, everyone has a price.
The common upward bump is partially because, why would you IPO if you didn't think there was long value? But also (I think) because in the first few days there isn't that much interest (volume of shares that are 1. tradeable and 2. which people want to let go of ~ IPO price), so the supply is constrained and the supply/demand value dynamic is biased up.