They are still (ostensibly) the subject matter experts so politicians defer to them. This in itself isn’t a problem: they
should defer to experts on complex matters. And often these experts
are organised in industry interest groups. The problem arises when opposing view-points are downplayed.
In the current case this is done because the industry interest groups backing the legislation are predominantly European content rights owners. Whereas the interest groups opposing the legislation appear mostly organised by non-EU groups, and therefore thus are less of a concern for EU legislators, and potentially don’t have the same kind of immediate access to them.