I suspect a big part will be that our currency is devaluing incredibly quickly, MG I assume use CNY, what we've agreed to pay them has dropped near on 10% since the time they likely set the price. So they're going to 'get' 10% less money from us once exchanged back to CNY.
In addition, their costs have gone up, both in components they buy, their own energy costs, shipping costs and likely labour costs too. If they have tonnes of orders... where would you rather sell, where you can get the most money obviously.
Wouldn't be surprised if some multi-marque dealers are also struggling or even going under / focusing on the brands they can get throughput with.
Not justifying the actions, but there are certainly numerous potential reasons to answer the 'why' question
Edit - Currency could be a non-issue, if they pay for hedging with another firm... if they do or not who knows (or the cost to maintain it could be becoming too expensive due to them breaching the time to supply the goods etc)