I heavily edited the original post, which may clear some things up.
Responding to your questions—
I do NOT know why they didn’t move the tourney to a playable venue in Philadelphia. There are several options, including even other grass fields that might have handled the weather better
It might be that JHU wasn’t considered because it would’ve given them “home” field advantage and, as the lowest seed, they hadn’t earned the privilege.
To be fair to the conference its member schools were allowed to compete in 20/21 but some of the conference members chose not to. Hopkins, for example, played and they ended up in the ‘21D3 world series.