I was under the impression that MEGA already has end to end encryption, so wouldn’t it be redundant to use cyrptomator on top of it?
Yes, MEGA has end to end encryption. But the scope of Cryptomator is that to block vendor (Such as MEGA, Google Drive, Microsoft OneDrive) to access our data.
Simply in this way only we can access our vault and our data.
If MEGA is end-to-end encrypted how could MEGA access our data?
They claim they can’t.
So from my point of view its a matter of trust in their encryption architecture when you decide if you want to use them with or without an additional encryption by cryptomator.
Ok, I get what you’re saying. 
And I suppose trusting cryptomator isn’t an issue since it doesn’t connect to the internet.
Cryptomator isn’t an issue, because it’s open source and in theory you could validate it.
On the other side there is rclone with an reimplementation of the MEGA API. I took a (really) quick look at the code and could not find any encryption code in it.