While theyre fairly powerful, its their effect on perceived barrier-to-entry that really posed a problem because casual players watching Commander games in passing could reasonably assume that they needed hundreds (now thousands) of dollars in Power-9 mana as table stakes, just to join the format
we (the PFP) want to make sure voices are heard, and to ensure the format is in safe hands." Pauper originated as a digital-only format on Magic: The Gathering Online in 2008, but has become more and more popular in both digital and paper formats since then, and became a sanctioned MTG format across MTG and MTG Online in 2019
The only reasons it isn't higher are because it requires a costly six mana each turn to pull off, eating into resources you could be spending winning, and because needing two colours in your colour identity limits the decks it could fit into
And finally, one of the better Merfolk commanders to ever be printed, Kumena, Tyrant of Orazca, is also included in case you want to swap out commanders, giving you some incredible power in the Command Zone.