My thw longest streak is 57 in wild format while just 7 in modern format.
I think sometimes we get continuously weak opponent that's why we able to make such a long streak. Otherwise, it is not possible to win continuously over than 50 battle for 20 battle. When I made by longest streak that time I was continuously getting one or two level summoners from opposition team. It could be more than 80 streak but I lost one Battle after 57 battle and again continuously won 27 battle.

In previous season I tried a lot in Modern format but could not touch 1K rating.
You are really doing good in modern format.