If the competition for JEE mains is increasing every year then why did the closing ranks go significanty higher for NIT's and IIT's in the year 2019 as compared to previous years?What will be the trend in 2020?

In the past few years trends for engineering has been decreasing if you look at the number of candidates appearing for JEE main and then you can see that there is change in the number of candidates appearing for JEE.

The other factor is that the number of seats are also increasing every year in IIT as well as in NIT because many IIT have increased number of seats and their program and some IIT have introduced new programs every year there for the number of seats has gone up and therefore the closing rank has also been because many ideas have increased number of states and their program and some items have introduced new programs every year therefore the number of seats has gone up and therefore the closing rank has also been increased.

Cut offs change every year depending on total no.of seats available. difficulty of the exam, previous year cut off trends, no.of Candidates appearing for the exam and no.of Candidates applying for a course. As much as the no.of Candidates applying for JEE are increasing, so are the no.of seats available. The cut offs decrease with the increase in no.of seats available and vice versa. Now lower the cut off, higher the closing rank. The trend might be more or less the same with a difference of 10-15 marks.