Why does it take so long to cap an oil well?

typically it does not, however the one you mention and the current one are very very deep, 2 miles and one mile, under water, so you cant just go down there and turn it off, it is too deep. regardless they should have backups and fail safes in place if they are drilling that deep underwater, which they don't, because in america the government likes to stay out of business, which most of the time is good, but can be to our detriment, in this and many other cases... housing bubble, stock market etc etc