I disagree with the fact that the long queues is the reason for the low Twitch viewership and let me explain.
First you have to think why we have such long queues in the first place. Its cause Ranked has low population and why is that? Cause people don't want to deal with the complexity of ranked and they get intimidated by it.
Smite's structure regarding having multiple game modes is the main reason why the MM is so messed up if you compare it to other Mobas. In other Mobas a new player is going to start by playing the main mode and as he plays casually he will reach a point where he will want to try the Ranked mode. In Smite a new player will have his first experience with Smite by playing Arena mode and by doing that he will prefer to stick to Arena mode where he is having fun and its way shorter rather than having to learn the ins and outs of Conquest. First impressions is a big factor and if a new player sees that he gets more fun out of Arena mode rather than Conquest he/she will never bother to queue Conquest.
That factors also as a reason for the low viewership in Twitch. Casual players is the very base of building Esports and if a big number of your casual audience plays a totally different game mode than Conquest then that means that they have absolutely no reason for tuning in to watch Tournaments or Pro players stream a game mode that they don't even play. The playerbase is so divided that if you ask 100 random Smite players which one is the favorite game mode I'm sure you will get mostly different answers from each one and that's a big problem for a game that's basically is an Esport.
Perfect example is the first day of the Spring SPL where Smite had over 20k viewers on Twitch for the SPL Tournament cause Hirez put the SPL ticket in order to incentivize casual players to watch the SPL. As the weeks went by and most of those players got their rewards, less and less players tuned in to watch the SPL. Twitch numbers dropped from +20k to 10k cause for them there was no point to watch anymore since they got their rewards, those players have absolutely no reason to watch it cause they can't relate to what's happening on screen since they play other game modes outside of Conquest. It's like if you were a basketball player and I asked you to sit and watch baseball that you never in your life played before.
TLDR;
LoL's new player experience= Casual Summoner's Rift--->Ranked Summoner's Rift-----> Watches Twitch Streams in order to get better from Pros
Smite's new player experience= Casual Arena or Siege or Assault - Isn't interested in watching Pros cause he doesn't have anything to relate to them
Smite's new player experience= Casual Arena or Siege or Assault or Conquest ----> Ranked Conquest ----> Watches Streams in order to get better
The fact that people that play the same game can't relate to each other cause they play a totally different mode speaks volumes why the Twitch viewrship is low