Jack Ma said on an interview that he don't know about Bitcoin at all, so how can he come up with the conclusion that it is a bubble if he doesn't even know how it really works, lol. It is obvious that he looks at Bitcoin as a competitor of his online payment processor called alipay, so I really don't care on what he said about Bitcoin. They are studying on how they can use blockchain in the future, of course to create a new cryptocurrency or implement it with alipay. So what do you expect him to say about his competitor.

This is what he said:
"I don't know about Bitcoin at all. I'm particularly puzzled. Even if it can really work, the rules of global trade and the financial system will be completely changed. I don't think we are ready. So I'm still paying attention to Alipay... to the US dollar, and the euro. We have a team that studies blockchain, but Bitcoin is not something that I want to pursue. We don't care about Bitcoin."
Source: https://cointelegraph.com/news/e-commerce-giant-alibabas-jack-ma-says-blockchain-is-not-a-bubble-bitcoin-is