I don't think this is some conspiracy or anything, they just released a new version[0] and it's possible it broke something. Also, it's still available at the EFF website[1], and if you look in the FAQ, it's not available in the Mozilla store either[2], so this may have been intentional on the part of EFF.

[0] https://www.eff.org/files/Changelog.txt

[1] https://www.eff.org/https-everywhere

[2] https://www.eff.org/https-everywhere/faq#amo