No, as it stands it is irrelevant. Only the presidency changed but there is no civil war. Let's not start spreading unrelated excuses to justify a military intervention that would do more harm than good.
As it stands, the Nigerien military has also explained that there had been roadblocks in the fight against jihadism because they were not allowed to coordinate with the new governements of Mali and Burkina which have veered against French interests. That was one of the main reasons given for the coup.
It has nothing to do with too many people being born.
Which countries with such policies are you speaking of by the way? (I'm curious, I honestly don't know)
Besides, Nigeriens are currently 25 million which is less than half of the French population in a country that is twice the size.
Poverty didn't start yesterday, nor did the exploitation of natural resources. How is that country so poor and others such as Qatar aren't?
It's impossible not to notice that former French colonies are often poorer than their British, Italian (Libya before the French, once again, pushed for a military intervention and embarked the US in that campaign) or Portuguese counterparts.
The only way fertility is problematic is that the population is young and the infrastructures that should have been built AND maintained... haven't. Along with education and the health sector.
All the more reasons to understand why they can seem to resent the French government (and not France in general as is depicted in some media).
Frankly, if solutions haven't been found after all these years, they simply haven't been sought. Going from first principles, if one wants to solve migrations and whatnot, just let them develop themselves properly.