From Coinbase to their Wyoming customers,

"Although we strive to provide continuous access to Coinbase services, Coinbase is indefinitely suspending its business in Wyoming.

The Wyoming Division of Banking has recently communicated regulatory policies which we believe will render continued Coinbase operations there impractical. In particular, we understand that the Wyoming Division of Banking interprets the Wyoming Money Transmitter Act to require licensure of entities which offer hosted wallet services, and that as a condition of such licensure, licensees must maintain dedicated fiat currency reserves in amount equal to the aggregate face value of all funds held on behalf of customers. Although Coinbase securely maintains 100% of all customer funds, it is impractical, costly, and inefficient for us to establish a redundant reserve of fiat currency in equivalent value.

We understand this suspension will inconvenience our Wyoming customers and we apologize that we cannot currently project if or when our services may be restored."

In a nutshell, it was state government regulation that forced their hand to withdraw from Wyoming.