Good point.
As you know, if you read this thread, I am not a big fan of Grayscale.
But they actually cleared the way for the new vehicle, showing that the market wanted a lean, effective, safe and tax-efficient way of storing bitcoins.
Of course, as more and more competitor start flowing to this new honeypot, Grayscale is going to lose market share, but I think the market will eventually get bigger and bigger, so they will be able to manage their competitive advantage.
Think about Tesla, the carmaker, not the bitcoin investor. Every time a new competitor in the industry is launching a new model the press calls that a "Tesla killer" when in reality is an "ICE Killer". Tesla could lose market share in the electric industry but can thrive if the industry gets bigger and bigger.

Same things for Grayscale: for sure more competitors can join the market, but the real losers will be those standing out of the market, not Grayscale.