Not only are people reporting different symptoms, but it has also been seen that the variant exposes healthier age groups, once considered to be relatively safer at higher risk.

While a lot of research is underway, one of the prime reasons why the new variant is able to attack the body in such a contagious manner is because of the spike protein present on the surface, which can surpass protective antibodies and defence lines quicker.
This is also the reason many feel the new vaccines may undermine the current vaccines, or require stronger doses right now.
Secondly, another reason behind delayed consequences and a multifold rise in severity and complications is faulty testing. While the viral infection can be picked up by any standard PCR test, the variant can only be confirmed via genetic sequencing, which is a tad bit harder right now, in testing times.
Since the virus variant is also capable of imposing new symptoms, or start off with different symptoms than before, many, unfortunately, get misdiagnosed and end up suffering from complications later.