Due to the high cost of energy we will shutdown your server on April 4th

Probably the hardware was already used when you got it. Stuff like SSDs tend to wear out and usually when you rent a cheap server, you'll get used hardware in the first place.

That said, their communication was bad. They should just have offered to upgrade to new hardware for a 50% price increase if the customer wants that. But I see little ill will in their behavior. Electricity prices did roughly double for them, and so must their prices.

This sucks and it is surprising how badly they handled the situation. They should at least offer existing customers priority for contact renewals. That's customer retention 101.

Having to hike prices due to rising costs is understandable, and maybe they found it highly unlikely that low-cost clients would convert, but if you don't propose you can't retain. And more importantly the company has taken a reputation hit, very unprofessional.

Why would France's energy prices increase 50%? They have majority nuclear power.