It's business and it's all about numbers. They couldn't just watch their competitors list then token while they did nothing. After seeing one of the most cautious exchanges like coinbase list them. It no surprise that Kraken have also decided to do the same
Today when I get login into my account, I saw a pop-up window regarding the start of SHIB funding. Trading hasn't started yet, but because SHIB wallet is open and ready to accept deposits from any SHIB holder, the time is not far off. In the meantime, I'm curious to see which pairs Kraken will open/ have available and I don't find it strange that they decide to list it. As you said, SHIB is another prospect/ asset for them that can bring more income. Easy and simple.