If it helps, I believe it was a guy from DK Vine having some sort-of source on the subject, and he spoke about it in this podcast I believe:
https://www.youtube.com/watch?v=gqYnzuV6Lsw
Unfortunately, it's over 3 hours long, and I don't remember the timestamp; I just remember it from 2018...outside of what he said, I only remember vague stuff about the time, and it won't help, but it may have been somewhere in the middle of the stream...
Considering it released earlier in 2018, in May, it's possible they didn't want to hold off on it very long. The dude in the podcast also mentioned Nintendo wouldn't let them use K. Rool when they wanted to iirc, though I think it was that they wanted to use him in their new DK games originally, only for Nintendo to say no.