The Dutchman became the first Premier League managerial casualty of the new season following a disastrous start to the campaign, which has seen the Eagles lose their first four games in a row without scoring a goal.
In an interview with Dutch publication Voetbal International, Ronald insisted that former Ajax manager Frank had not been given enough time to impress his methods upon his Palace players.
"It's very sour when you think about the original appointment," he said. "Crystal Palace wanted to play football in a different way, play more of a possession game. That does not work from one day to the next at a club that has always played in a traditional English way. Last season too under Sam Allardyce.
"Frank needed time to sharpen the game that Crystal Palace wanted in the future. The club emphasised when he was appointed that he would get the time in that process. If you take Frank as a head coach, you know as a club that you are getting whole soccer philosophy at your club. That seemed to be exactly the intention.
"Unfortunately, the chairman made a panic move and Frank has suffered a new blow abroad.
"One thing is clear: today's football world is hard and ruthless. If you do not win, then you are out. But I also need to be realistic: Frank has not succeeded abroad."
Former England manager Roy Hodgson is expected to be appointed as De Boer's successor in the next 24 hours.