I think it's legitimate to suggest that some of the more extreme elements of the BLM organisations demands could increase the likelihood of bad behaviour towards the police.
A look at the BLM UK twitter page shows that they suggest defunding/abolishing the police. They are also trying to Stoke up bad feeling towards the uk police.
There have been attacks against police at lots of the blm demos (admittedly by a very small minority).
When hatred and mistrust of the police are being actively formented by a high profile organisation. Its not completely mental to question if this has an impact on events like the one in question.
It may or may not have been linked. But the scummier elements of society are more likely to be emboldened if they feel like they have the support of the community