My new laptop was stolen from mail box

You need to contact Best Buy and/or their delivery service - they are the ones who left the package. And, you bought it from Best Buy, so Apple has no responsibility. And, if you had not activated Find my, there is nothing stopping the thief from using it. It cannot by found by serial number.

And, is your mailbox not locked? File a police report and argue with Best Buy and their delivery about leaving an expensive laptop somewhere in an open location.

We are not Apple, this is a user forum. Have you filed a police report?

...their delivery about leaving an expensive laptop somewhere in an open location.

It's a COVID-19 side-effect – delivery people would prefer to avoid the risk of frequent customer contact. When I ordered my 16" MBP, it was shipped with a Signature Required delivery option...but the delivery service just left the package in front of my garage (fortunately, I live in a very safe neighborhood). Similarly, our monthly wine club deliveries require a signature from someone over 21, but likewise the delivery service just leaves the wine shipments on our porch (different shipper than who dropped off the MBP, but the two of them are the two big ones).

Not so sure it can be blamed on the pandemic - we're had lousy service for longer than the pandemic. I find it absolutely irresponsible to ship and/or leave anything +/- $1,000 in a publicly accessible area for everyone to see (and steal). The "porch pirates" are just waiting - especially in "safe" neighborhoods as they assume that the takings are possibly more worthwhile to steal. We're in one of those and the Ring app shows amazingly busy nights from neighbors.