Saying why you quit the last job 

I was recently fired, and I’m finding it tough to answer questions regarding my unemployed status to potential employers.
I worked for my last company for 10 months. My numbers were high and my clients had only positive things to say regarding my service to them.  I always knew that there were some issues with my fit in the company culture.
Out of the blue i was asked to meet with my line manager and his manager for a drink one evening at the hotel they were staying at. I met with them and they were extremely awkward and i knew that something bad was coming. They said that I was being asked to leave the company effective immediately and that i would be paid 3 months salary. I asked what the reason was and both guys eye-balled each other and didn’t reply.
So I wished them well, asked for a good reference from my line manager, and I walked out.
I have been in touch with some potential companies and some headhunters with regards to new possible positions and the first question that always comes up is “why did you leave your last position after such a short period of time?” With some headhunters I have been honest about what happened in the hopes that they may be able to offer some advice from their expertise but most of them just say that they will find it hard to place me in a new position.
One head hunter advised me to say that my role with the last company was a “set up” role where I was employed for one year to establish the brand in the market using my industry links, marketing skills and product knowledge and that I was now free to pursue other options now that the set up was established.
Do you have advice on how I can overcome this hump?