Any good pieces of journalism on why this mass immigration has been happening?

Is it an organic process? Or Are there various NGO's or government programs or UN programs trying to suck in immigrants / encourage and enable people to move to "the west"? (who would not have considered emigrating without the intervention of these organizations)

Basically is the bulk of this immigration happening out of the own free will and self-determined decision-making of the immigrants or are there third parties doing their best and succeeding in making the immigration to happen?

I used to not really think about it and I guess I assumed it was a natural / organic / not-artificially-induced phenomenon but now I'm not so sure.

Would it make a difference in your view which of these scenarios, or in what proportions, were reality?

Also is it known what percentage of the immigration that Europe is dealing with is a result from USA's ( or NATO's) war activities and USA's efforts of "spreading democracy" (and the ripple effects of these / effects downstream of these)?