The question is what counts as a crisis.
Haidt presents datasets that are very short. The graphs begin in 2004. Teens have been depressed for a lot longer than 20 years. It's hard to know what the natural variance of this statistic is given just his articles.
If you look at longer term US suicide stats (stratified by gender but not age) there's quite a bit of variation over time.
https://www.statista.com/statistics/187478/death-rate-from-s...
The 1970s were really rough for women, but not men. 1990 was rough for men but not women. These graphs show that variance can be pretty high when taking the long view. Current overall suicide levels aren't anything special, even though they've been going up for decades (watch out for the non-linear X axis).
If we look at the 10-14 girls dataset that Haidt picks where the change seems most dramatic, it goes from 1 per 100,000 to 2 per 100,000. Very few people commit suicide at that age, fortunately. We're talking on the order of 100-200 girls in that age range per year in the entire USA. At these low initial levels, even very small changes will look big on a graph. Every death is tragic, but if "crisis" now means something that affects such an truly tiny percentage of the population then almost anything can be a crisis.
The other unrelated issue is that if you look at his graphs, self harm and suicides started going up in 2007, not 2012 as he claims. I don't see how you'd pick 2012 as the inflection point if not trying to force the smartphone narrative.