This drops off far faster than the uniform case, once 2050 is reached.

The intuitive explanation for this behavior where the normal distribution drops off faster is because it makes such strong predictions about the region around 2050 and once you've reached 2070 with no AI, you've 'wasted' most of your possible drawers, to continue the original blog post's metaphor.

To get a visual analogue of the probability mass, you could map the normal curve onto a uniform distribution, something like 'if we imagine each year at the peak corresponds to 30 years in a uniform version, then it's like we were looking at the period 1500-2100AD, so 2070 is very late in the game indeed!' To give a crude ASCII diagram, the mapped normal curve would look like this where every space/column is 1 equal chance to make AI:

2k/2k1/2002/... 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 etc.