https://support.google.com/maps/answer/14169818

Update Google Maps to use Timeline on your device

Important: These changes are gradually rolling out to all users of the Google Maps app. You'll get a notification when an update is available for your account.

Location History is now called Timeline, and you now have new choices for your data. To continue using Timeline, you must have an up-to-date version of the Google Maps app. Otherwise, you may lose data and access to your Timeline on Google Maps.

Timeline is created on your devices.

Basically they're getting rid of the web version because they're moving the data to being stored on local devices only. Part of this might be because they got a lot of flak for stuff like recording location data for people who went near reproductive health clinics and other sensitive things. They can't be forced to respond to subpoenas for data if they don't have the data and can thus stay out of it, so I wouldn't necessarily say it's all that altruistic on their part.