Ireland has to rush through supporting legislation because the responsible minister is apparently useless. The GAA have agreed to let them use their stadiums, so they're well sorted there. Just an issue with hotels and public transport. But New Zealand coped, so...
France had it only a decade ago, so it's still fresh in everyone's minds.
South Africa couldn't cobble together the cash for a Commonwealth Games bid. They've also got serious security concerns. Enough to make a bus trip in Egypt or an antiquities tour through Syria look enticing.
Ireland's by default. I should imagine it would be great fun too. Although three hosts in a row that don't get out of the pool stage wouldn't be a good look.