This alone rules out the potential for it to have been a malware attack
No it doesn't. Screen capture malware could have stolen your seed phrase as soon as it was displayed to you.
but to be certain that there was no malware like a keylogger, I ran malware bytes and avast, both of which came up with 0 detections.
All that these can do is test software against a known database. They are not infallible, and there is malware out there which can evade such detection.
No, I just downloaded it for the first time. I assure you, the download was the official one
Again, this doesn't mean anything. Exodus is closed source, so actually you have no idea at all what you downloaded. Perhaps some malicious Exodus employee inserted some code to steal coins. Perhaps the app pulls from some library which has been replaced with a malicious version. Perhaps their download server was hacked and you downloaded a malicious app even though you were on the official site. Perhaps you weren't on the official site at all, and were redirected to a clone site without realizing. Perhaps you were victim of a homograph attack.
This is why it is important to use open source wallets which can be reproduced from the downloaded code, and which can be verified against signatures of their developers. It still doesn't make you immune to a malicious wallet software, but it certainly helps.