A lot of people simply did not read the article. When COVID hit, rental agencies sold off much of their fleet since there was no demand, it cost them money to own and store the cars, and it earned them much needed cash by selling cars. They have not yet replaced those cars, and now that demand is picking up, during hot travel times, demand far outstrips supply. This is what is causing the spike in car rates and it is entirely dependent on timing and location.
The article suggests that you book your rental well in advance to avoid price spikes.
The article also notes that this issue may last all year as it will take time for rental agencies to build up their fleets. This is compounded by issues with new car supply. And agencies are struggling with cash to buy new cars (Hertz is still going through bankruptcy).
Although the article does not mention Europe, the same situation is likely to impact European agencies as well.