Why do we have to wait 60 days between each domain transfer?

Here is a Guardlex article that claims that it is to prevent domain hijacking:

Once a hijacking has been discovered, the responses to it tend to vary. The registrar is sometimes able to return the registration to its original state. However, if the domain name was transferred to a different registrar, this can prove to be difficult. This is especially true if the registrar is in a different country. There have been many cases where the original owner of the domain has not been able to regain control over a domain that was hijacked.

The Internet Corporation for Assigned Names and Numbers (ICANN) requires that there must be a waiting period of 60 days between the time that the registration information is changed and when it is transferred to a different registrar. By doing this, the process of hijacking a domain becomes a tougher task. This is because there is a good possibility that the original registrant will notice the problem during the 60-day window and alert the authorities about the issue. A domain that has been transferred is also a lot harder to reclaim. This is another reason that this method reduces the risk of domain hijacking.

If a domain name were hijacked and the hijacker were able to transfer it several times, getting it back would need to involve all the registrars to which it was transferred. The process should be simpler if there are only at most two registrars that need to cooperate for the solution.