Exchanges have very clearly defined rules for when they will halt trading. With clearly defined rules, you always know why a stock was halted, and when it will resume.
Robinhood has no set rules, and it was impossible to predict when or if they'd halt purchasing shares. It was also not possible for Robinhood traders to know when trading of the stock would resume.
Also; Robinhood didn't halt the trading of GME, AAL, AMC, BB, and others. They just halted the purchasing of new shares. Robinhood tried limiting who could buy shares of those stocks to only the hedge funds. That would drive the stock price down, thus manipulating the stock price in the favor of Citadel / Melvin and their short positions.