Dogecoin started in 2013 as a joke or parody, making fun of the cryptocurrencies. Because of that, it was getting attention on social media and was becoming more popular. Later the popularity of Dogecoin was increasing because of encouragement from Elon Musk and some other celebrities.
In the first half of May, Tesla announced it will stop accepting Bitcoin for car purchases, because of Bitcoin's high energy consumption and environmental impact. A couple of days later, Elon Musk has announced on Twitter, he is working with Dogecoin devs to improve its transaction efficiency. According to Musk, Tesla wants to use cryptocurrency, that is more energy-efficient.
The price of Dogecoin is going up also because of more companies accept it as a payment.