The con has now apologised for the captioning. They rushed it out last night and I thought it could have been clearer, and that it didn't really understand the access issue of completely pulling captioning. Someone in Fans For Accessible Conventions said they spoke to the con-chair this morning and he now does understand the issue, and any surplus they pass on to future worldcons will probably come with a recommendation it be used on access/captioning.

https://dublin2019.com/apology-from-the-chair-for-the-problems-with-the-close-captioning-during-the-hugo-awards-ceremony/