How are Bertelsmann left-leaning?
But as the sibling comment notes, in other areas they're not at all left-leaning, e.g.:
Arvato, a division of the Bertelsmann Group, declared the privatization of public services a strategic business area.
It should not surprise anyone that characterizing their politics on a one-dimensional left-right spectrum is inaccurate (findings such as https://arxiv.org/abs/1904.12320 notwithstanding).
Before Occupy Wall Street went down in flames, (actual, hard) leftist liked to critique the false dichotomy between what’s presented as left-wing and right-wing politics in western democracies, and they were very right to do so. What I wrote here about media applies to politics just as well: https://news.ycombinator.com/item?id=28904146