> How do you know all this?
His involvement in the early days of Friends was covered in some depth in I'll Be There For You: The One about Friends - which I had read when it was published a couple years ago and highly recommend if you're interested in this type of stuff.
The person who wanted to take them out to Vegas was James Burrows who had been one of the creators (and primary directors) of both Taxi and Cheers, so he knew a thing or two about what makes for successful television and he recognized Friends was most likely going to be a huge success.
The story of this evening is told in some detail in I'll Be There for You: The One about Friends, which I highly recommend reading if you're interested in some of the background of the show.