That’s my guess is as well - good ol out of funds. Maybe there’s no desire to fund this project.
Discussion
I think it's more the juice not being worth the squeeze. afaik the company Mutiny will still be around but they are shuttering the wallet to focus on other projects. the Mutiny Wallet is OSS and can be forked at any time. it's also easily self hostable and can be hooked up with an LSP like Zeus' Olympus to get much of the functionality it has.