Technology due diligence should not happen after you have decided what you want
Technology due diligence should not happen after you have decided what you want to do. By then it is not diligence. It is justification with a budget line.
The pattern is familiar. The executive team sees a demo. Someone falls in love. A vendor is chosen in principle. Then, because governance requires it, a review is commissioned: reference calls, a security questionnaire, a look at the contract.
Every question in that review is now being asked by people who want the answer to be yes. The reference calls go to customers the vendor chose. The security questionnaire is completed by the vendor. The contract review negotiates price and misses the exit clause. Findings that would have killed the project a month earlier are now "risks to manage."
This is not a character flaw. Once people have committed emotionally and publicly, evidence gets sorted into support and noise, and everyone in the room can feel which pile a finding belongs in.
The only fix is sequence. Diligence before preference. Write down what would disqualify a vendor, before you have seen any. Write down the number the project has to earn, before anyone has estimated it. Decide who does the independent read, before there is anything to read.
Then look at the demos. The questions will already exist, and they will be the questions you would have wanted to ask, rather than the ones that let you sign.