The quality of Google Map is better than others because it has more users, and thus better
input data. And that's the real problem - competitors cannot improve improve their product without better data, and so users find it inferior and avoid their product / service and turn back to Google Maps (which allows Google to improve their product further and take a lead). Note though that Google has another edge over its competitors - (1) Android OS has been collecting geo-location data even if you don't use Google Maps and (2) Google also gets their competitors data if a user uses a competing map app on Android OS.
Google search is also in a similar position - the vast amount of users means its competitors just cannot improve their product because users become disappointed with the quality and stop using it, thus denying them a chance to improve their product.
The old solution to prevent anti-competitive behaviour and foster healthy capitalism was to break them up. But for more modern problems like this, I think a different approach is also needed - we need to force such monopolies to also share their data with the competitors, till the competitors become large enough to compete with them on their own.
(For those seeking a decent alternatives to Google Maps, I recommend Here - https://wego.here.com/ - it was owned by Nokia before they sold it to a consortium of European automobile manufacturers and is quite good).