In the UK the public overwhelmingly support the age controls, so even political parties who would otherwise oppose it just stay silent, because the public narrative
You have to shift the narrative. Farage does this - he's finally after 20 years managed to get elected to parliament, he's head of a company with 4 MPs, same say as the Greens, about the same as the nationalists, yet for 20 years he has steered the conversation and got what he wants time after time
The playbook that was overwhelmingly successful for making Brexit happen is being used again, but this time for immigration.
The fact he got elected as MP only serves to give credibility to his backers' narrative, given that he does not serve his constituency and is too busy schmoozing the US right wing. At one point in time he would have been forced to resign in disgrace for backroom dealing like this (as previous MPs have before).