In the light of means considering certain knowledge/information (synonyms: in consideration, in relationship to).
In the light of what you’ve just said, I decided to give you another chance.
In the light of last week’s lecture, all the students were allowed to submit their papers later.
On account of means because of/due to/ as a consequence of.
He did not come to the meeting on time on account of his recent family emergency.
We couldn’t go to the beach on account of the bad weather.
P.S. On account of and because of are synonymous and are usually used interchangeably, BUT because of is more appropriate when we are talking about facts. The water boils because of the heat.
