The Dutch legend, capped 112 times for his country, took over as Palace manager in June but four successive league defeats without scoring saw the 47-year-old sacked yesterday.
De Boer did guide the Eagles to a 2-1 victory in the Carabao Cup against Ipswich but his time at Selhurst Park has been shortlived and former England manager Roy Hodgson is favourite to replace him.
Albion boss Chris Hughton said: "The reason why it hasn't surprised us is there was so much speculation before but it's a real tough part of the game.
"It's a consequence of how the game has changed that somebody can lose their job four games into a season. And it's a consequence of the pressure and how the job has changed but as a manager and somebody that is involved with the LMA (League Managers Association), it's not something you want to see.
"It just makes it even harder for managers."
Hughton added it sometimes takes time for new managers to get their point across to players and de Boer adopted a different style of play at Palace, compared to previous boss Sam Allardyce.
Hughton said: "What can happen is managers can come in and have an instant impact but sometimes that's not the case. Sometimes they need that little bit of time to get to know the players, for them to adapt to a system. Managers, at times, need time as it doesn't always happen instantly.
"That's something in the game that will never change. For as many managers that have a great start, there are just as many that don't.
"It's a consequence of our game but I'm very disappointed to see it as a fellow manager. It just goes to show how difficult this job is."