Why is everyone suddenly running Lumi?

I was running a Lumi lead with Fives, Rey, RG, and Leia and was able to keep consistently in my arena's top 20 ... I recently switched her out for St Han and have been able to break into the top 10 .... She is a great character and definitely underrated ... but for arena there are probably more effective choices (at least for those who want to move up in rank ... just running whom you like is also a valid factor, imo).