The bookmakers are strictly business oriented people, if there is a stats that proves Nigeria has big upper hands to win this game, they wouldn't give the 1.9@ odd because if Nigeria wins the match and many people win this game, they will be questioned on their decisions to give Nigeria such odd instead of Nigeria. More over, it can get reduced or increase before that day as they get some hints and information, there could be one player that can change everything about the odd.
Nigeria and Rwanda don't really have much historical data, the ones they have in the last 5 matches held, Rwanda lose a single game, they draw 3 and while Nigeria win one as well. This is a tigh stats in my opinion but what surprises me is that even by ranking, Nigeria isn't there mate, Rwanda is rank 122 and Nigeria is rank 31 place. Unless they are using home game as an advantage here, there is nothing special about them, we shall find out that very day.
Bookmakers are used to trick gamblers with their odds allocation to teams just to cause confusion. That 1.9 odds given to Nigeria at the moment will push some people go give Nigeria a direct win. I mean people that normally place their bet based on smaller odds and not by records or recent developments in a team. First thing to consider here is that Nigeria would be playing under a new couch for the first time he's been appointed as the new head coach and he's yet to figure out his best men.
Quite alright, the super eagle has strong squad but you don't expect things to be the same watching a new coach for the first time. Secondly, the entire eagle performance in the ongoing qualification games hasn't been good enough and Rwanda is the one occupying the top table. If Nigeria is lucky enough, they would probably get draw from this upcoming match. I personally have no confidence in them winning against Rwanda at this time despite they have been favored by bookmakers.