In my opinion (though, I'm not a native-speaker), both Present Simple and Past Simple are ok in this sentence.

You can use Past Simple if you want to emphasize that the event was in the past, and you can use Present Simple if you want to indicate that from the point of view of the present there is indeed none greater than that wave of migration.

The problem can be solved on the basis of idiom ("more than") and modifiers (the opening phrase "of all the vast tides..." shouldn't modify the place-holder "it") as was indicated earlier in this thread.

I was mistaken. The tense matters. See here: https://forum.wordreference.com/showthread.php?t=2812384

Of all the vast tides of migration that have swept through history, maybe none is more concentrated as the wave that brought 12 million immigrants onto American shores in little more than three decades.

More… than is the correct idiom
More… as is not an idiom

(A) maybe none is more concentrated as
More… than is the correct idiom
More… as is not an idiom

(B) it may be that none is more concentrated as
More… than is the correct idiom
More… as is not an idiom

(C) perhaps it is none that is more concentrated than
It is an emplty it OMG this is a train wreck.

(D) maybe it is none that was more concentrated than
It is an emplty it OMG this is a train wreck.

(E) perhaps none was more concentrated than
This is the correct choice