From what I have noticed regarding Newcastle decline, it is because they did not make good use of the transfer market season and had too much confidence in the squad they had last season. Meanwhile, other teams that are currently at the top are making improvements so that they are at least able to maintain their performance in the EPL. Not only that, the strong reason behind Newcastle setback is the mental factor of the players, mental matters cannot be taken lightly, because speaking of the EPL you need to be mentally strong enough to be able to compete. As a result Newcastle lost its best performance, and we can't expect much from Newcastle club management other than having to go through a bad phase because of its own mistakes.
Newcastle's unwanted transfer mistakes have made this season not go well for them.
Actually for this season the steps taken by Howe are actually very good where they bring in several players including Tonali who in fact is one of the very good assets because at a very young age he became a promising player because of his good performance, it's just that there were some unexpected situations where Tonali had problems with illegal bets made him get problems and a ban on playing even until the end of this season he will not be able to compete which makes Newcastle experience problems in midfield because it cannot balance the squad because Tonali was included in Howe's previous plan.
This is what makes Newcastle troublesome even though their momentum last season was very good but because of some unexpected mistakes it made them this season experience destruction.