Calender Spreads in Futures

Hi,

I want to know what can be the reasons for increasing or decreasing the spreads between current month and near month futures.

I read about calender spreads on Zerodha Varsity.

NF Futres continuous chart which is determining when to execute calender spreads based on last 8 months of data.

https://divyankm.github.io/Stock-Exchange-Data-Analysis/html%20files/NIFTY_FUT_Calender_Spread.html

Snap-