I have a general opinion that I2P isn't very actively used in many applications, am I wrong? Not just bitcoin, but generally.
But if you search ".i2p" on the search column, it shows 0 node (which should be incorrect).
I think this can be manipulated, because there are multiple occasions where I 've known about .onion nodes that weren't visible in the bitnodes website. I don't know how it's possible, but I 've seen it happening. That's why people say that the total number of nodes is actually higher than the one visible on the website.