Why/how option premium change so fast in indices ?

[curiousv]

I see there is very fast movement on options premium particularly bank nifty ...But how does this change work?
I mean computers (algo) are doing this big volume trades or there are 100s of traders employed by big institutions are doing this ?
Can someone explain?

 

[AJK]

Option selling is the trend now, sometimes they don't need a direction!

 

[Praneeth Kumar]

One tip I would recommend is do check india vix before selling bank nifty options. If vix is starting to decrease in intraday then chances of premium decreasing is faster.