Why do acquisitions fail? What's your perspective?

I read a statistic today where the author claimed that fewer than 20% of all companies that are for sale ever get sold. I don't know where that number comes from (he didn't say) - and I have no way of knowing if it's accurate or not.

But let's look at it from another perspective: the success rate. Of the business owners with a company on the market, what percentage would you say actually succeed in getting a deal done? Your estimate could be based on your observation or from direct experience.

If you're so inclined, could you also say what you think are the most accurate predictors of success (or failure).

(Hat Tip to ^ redacted‌) who offers some ideas of his own - based on his experiences.)