> that makes the far-right parties grow stronger
That issue is just one of many that they use and abuse to gain popularity. They have also spread lies about vaccines. They promote antisemitism, xenophobia, hate against the LGBTI people, historical revisionism (e.g. they say nice things about the Nazis), etc. They are even fighting against the wind turbines (or, as Donald Trump calls them, the "wind mills"). You cannot satisfy their demands by "fixing" one issue. Because they will always find another. The more absurd one, the better, it seems. I think that the reason is that those absurd causes are supported by people who are easy to manipulate. They know it. And they abuse it.
> Why wait for these parties to use this issue to fuel their growth?
No one wants to wait. But at the same time, I have not yet seen a successful recipe on how to root out their populist practices and render them ineffective against the general population at large. Because, unfortunately, there is still a considerable number of people who are falling for it. And it seems to me that no politician or party so far has been able to figure out a reliable way to protect those who are most vulnerable from being manipulated this way.