There are both positive and negative opinions about him online. When I searched for further information about his centre, I may have identified the reason. Through his hard work, he has developed a huge organisation consisting of over 600 centres, mainly throughout Europe. It is a massive organisation with thousands of members and naturally such a successful organisation will invite detractors as well.
List of websites with positive feedback:
https://www.tsemrinpoche.com/tsem-tulku-rinpoche/great-lamas-masters/lama-ole-nydahl.html
https://en.wikipedia.org/wiki/Ole_Nydahl
https://www.scmp.com/magazines/post-magazine/long-reads/article/2087405/lama-ole-nydahl-talks-drugs-meditation-and-losing