hello community cryptomator please tell me why it is used aes and her ChaCha-Poly?
That’s like asking: Why does your car burn gas? Because it was (and still is) the available technology at the time we decided for a cipher.
Vault format 8 (to be introduced in 1.6.0) allows new cipher configurations to be added. At first, we will add AES-GCM as a replacement for AES-CTR-then-HMAC.
Maybe ChaCha20 will be the next alternative. It mostly depends on device- and library support.
Can’t wait for 1.6 then 
My personal preference would be twofish/threefish but obviously you can’t please all of us.
Just give us a choice 
Thanks for your hard work anyway.