Safari crashing regularly is not normal behavior. To have it happening on more than one machine is especially abnormal.
Along with the clear History suggestion you could try:
Enable the developer menu so you can "Empty Caches" --
In Safari on your Mac, use the developer tools to make sure a website you create works well with all standard web browsers.
support.apple.com
Use developer tools to create websites for Safari.
support.apple.com
Try after disabling extensions and plugins. If better, reenable them one at a time and test to find the problem child --
If Safari doesn't load a webpage, stops responding, quits unexpectedly, or otherwise doesn't work as expected, these solutions might help.
support.apple.com
Boot into Safe Mode and test, then boot normally. Note if there's any difference between them. (Sometimes problems can be fixed just by booting into Safe Mode then booting normally. Safe Mode has some maintenance and repairing abilities.) --
To help determine whether an issue is caused by software that loads as your Mac starts up, you can start up your Mac in safe mode.
support.apple.com
Create a new user account for testing purposes --
If an issue stops happening when you log out of your macOS user account and log in with another, the issue could be related to the files or settings in your user account.
support.apple.com
If you're using iCloud to sync between your machines, try disabling that for a bit at
System Preferences >
iCloud