That is odd, definitely. Like, yeah, as Superbird pointed out, Christianity and Judaism are both Abrahamic religions, so I guess you could sort of justify combining them into one category on that basis? But if you're going to do that, then why is Islam separate?
The list of religions also just generally looks weird to me, but apparently this is based on UK census data... The UK has a much more different distribution of religious affiliations than the US than I was expecting! Like, I was weirded out that there would be enough Sikhs for that to be considered a major category... then again I can't actually find any data that goes out to six different groups in the US (not including atheist/unaffiliated), so maybe it's actually the next major group after Hindu here as well, it's just so small that it's not usually reported. According to this Pew Research data, it would fall under "Other World Religions," as part of just 0.3% versus over 1% in the UK data.