How to get over imposter syndrome

I got promoted from manager to director position, well i don't know if that's a promotion because my director was leaving and I applied for his position and I got it. In my team, my previous role was quite a solo role, though I am a manager, I had no direct reports. Previous, I held senior roles in other orgs but here, it was just me. As a manager before, my role was quite chilled. Straightforward, not always busy and no need to intereact with others. So during some team building activities, I get to know with other coworkers from my team and have conversations and all. So, when I got this role, I found out my same coworkers (juniors)' behaviour towards me have changed. Dislike? Idk. I led farwell video to my former superviosr, and one of the team members wrote 'you are my only lifetime director' in their message. All department team members didn't write much but my own team members wrote messages like this, even in bold setences. Well, I know they have their time with him and liked him, inspried by him but I still feel a bit intimidated. The teams are already settled and I don't plan to make big changes. People are quite accountable for their work and all that. So, I really don't plan to make some changes at all. There is another person who on surface (during team meetings) would say 'yes', 'I agree', but when I personally communited one by one, he never followed my instructions or oppose my ideas. Never taken my words seriously either. Even when I first met him a few months ago, while I was still a manager and he was and still is a junior, looked at me and said 'I didn't know your existence' or something not polite during our first conversation. He still don't give me any respect. I reflected myself, did I ever did anything wrong or behaved not appropriately. Well, i don't recall any, especially my role didn't involve talking or communicating much with others. So, there was no such thing.
Anyway, the big boss also liked my pervious director. They worked for 7-8 years since the company founded. She said 'that was fresh' when I applied to my director's role. Did she not like me either? Gosh!

How do I overcome this imposter syndrome?