but all that was lost in the Revolution and he vowed he would never return
This may have been one factor. Another is that he had recently married his own cousin - a breach of the law which put the couple at risk of arrest. (Such a marriage needed a Consent Letter from the Tsar's Office, as they were well aware - which is why they bribed a drunken priest in an outlying suburb of Moscow to marry them. Technically neither was a resident of that parish, and so Rachmaninoff rented a room nearby, without intending to use it - so that he could claim to be a parishioner).
In hindsight, it's very probably that his life would have become difficult if he had not emigrated - but he couldn't have known that for certain in 1917. Unable to find as many commissions as he hoped - and sought out as a solo pianist to play the Prelude he came to detest - it can't be said that his creative life in America was a complete fulfilment of his ambitions either.
