Thanks Vishal and Praveen.
I also realized later that this happened most likely because: most buying happened in 1st 5 min only--so VWAP shot up in 5 min, but not after that.
This I feel is typical behaviour of retail, and not of smart money. Smart money tends to buy slowly at VWAP. But, retail would immediately rush in.
So my sensemaking:
Retail piled on in 1st 5 min--due to some news or pattern or level. But then Smart money/smart traders sold.
This is also visible in 1-min chart, where first candle itself is ~0.8%, causing a spurt in VWAP. Smart traders will typically not buy like this unless some big news.