Usually Lord Krsna attracts everyone. But here we see lord Krsna is attracted by these two devotees Srutadeva and Bahulasva.

The distance from Dwaraka to Mithila is something around 2200 kms and so many devotees have described how they have such wonderful qualifications. They were so much attracted and dedicated to the deities they had in their homes. They actually did not have time to travel to Dwaraka to take Darshan of the Lord. Everyone, even the saints and sages used to travel to Dwaraka to take Darshan of the Lord. But these two devotees did not travel to Dwaraka simply because they did not have time.

Why did they not have time?
Because the whole day they were engaged in serving the deity form.

And this dedication, this sincerity in serving the deities attracted the Supreme Lord Himself but then although they are pure devotees as it's mentioned by Srila Prabhupad they were simple devotees and that attracted Lord Krsna.

But even amongst pure devotees Lord Krsna sees that something needs to be taught to them.

One thing that we can learn from this is that no matter how well learned we are there is always something that needs to be learnt.