Why SIM has Re-sized and changed to Micro SIM then Nano SIM !!!!!!!!?

You might as well ask why SIM cards (credit card sized) became minSIMs. The answer would be exactly the same as why miniSIMs became microSIMs and why they in turn became nanoSIMs. All thT prevents further size reduction now is that the existing nanoSIMs are as small as present removable SIM technology allows without starting to trim away vitally functional parts.

The answer is simple: smaller SIMs mean smaller phones, more room for other components become possible, and provide potentially better sealing against ingress of dust and water as the SIM slot doesn't need to be as big.

You know the phrase "The bigger the better"? Well it's not the same for electronics.. China loves small things lol

So? Just trim the card.