OK, a slightly more serious answer---

Various ways we arrived at it

* We're Canadian. Winter is brutal.

* We rented a vacation place nearby in France in 1998 and loved it, allegedly the best microclimate in Europe.
We searched for a place to rent near that for a longer stretch winter 1999/2000, largely for a vacation and a millennium party, and loved it even more.
So when it was time to go back to Canada in April 2000 we toyed with the notion of moving there...but the tax situation in France is pretty brutal.
Monaco was only a few km away, how much worse could the weather be?
By June 1 we had made up our minds, looked at a place, made an offer, and closed the purchase.

* Around the same era we had looked at various tax free places, or nearly tax free, just toying with the idea.
One was the British Virgin Islands. There was a very attractive property for sale on Tortola, I remember.
But...what do you do after the first few weeks on a sunny boring island?
And no great "world city" is exactly close, either.

* Monaco is nice.
No tax, no snow, no crime. What's not to like?
If you get bored, you can be in London or Paris or Rome or Amsterdam by mid morning.

We have friends who moved to Grand Cayman fairly recently. No tax, weirdly good food, very nice people, and Seven Mile Beach (sadly lined with big hotels).
But other than the beach, MAN that is an ugly piece of geography and townscape.
And not exactly a hotbed of deep culture, either. Not for me. And most of stuff there is at least as expensive as Monaco, from taxis on up.

Jim