Exchange of information shifted from corporations to bank accounts. It started with FATCA and then become global through CRS. This made the banks far less attractive for tax evaders and money launderers, so they started leaving. With those customers gone, there weren't many left.
Another massive move was when correspondent banks were also instructed by regulators to de-risk or face penalties, meaning every little dodgy offshore bank suddenly had to make a lot more financial sense to keep around. It used to be that correspondent bank could more or less turn a blind eye︀ to what went on in correspondent accounts. When that changed and the correspondent banks were︁ facing responsibility for what went on there, they started kicking out banks that weren't worth︂ their while.
The barrier is finding a correspondent bank that wants to︇ work with you. The major correspondent banks have terminated relationships with practically all such banks.︈ In many cases, the correspondents aren't even banks but currency exchanges or payment processors, which︉ in turn may have relations with banks.
If you get a banking license in Samoa︊ or Dominica today and then go knocking on the door of major correspondent banks, they︋ won't even listen to you. You would need to have an extremely attractive business case︌ backed by large, safe clients and an experienced team (board of directors, executives).
That era︍ of offshore banking is dead. If you can raise 10 million, start a bank in︎ EU instead as this gives you access to SEPA and TARGET2. You'll also be far️ more likely to get correspondent relations for other currencies. Even doable with an EMI license in many cases.