They even noticed it before the FTX crash, but they believed in the exchange so much they didn't mind it. However, as far as FTX is concerned, there are many negative issues that may make them uncomfortable keeping their assets on the exchange so they choose to withdraw their assets to their respective wallets.
If indeed the FTX case has taught us about security, then will the percentage of trust in other exchanges have any effect. To this day how many exchanges are listed and how do they provide answers regarding the level of security, while the owner of Binance once said, that the exchange is not a place for long term asset storage (if my memory serves me correctly).
But as @mk4 says, these assets will be very easy to transfer back to the exchange when their holders start to trust the exchange again as before. For a while, the situation of centralized exchanges really lost a lot of holders as most of them withdrew their assets, but it will return to normal with time.
Exchange reputation has different levels of trust. When the FTX case starts to no longer be discussed in the public sphere and it no longer makes people feel afraid, it will return to normal conditions. On the other hand, many people are starting to realize that the exchange is not a safe place to store assets, both for the long term and in large quantities.