The 3 biggest browser engines are Gecko, Webkit, and Blink.
Gecko is the engine behind Firefox and is maintained by Mozilla, so it has a good number of open source contributors that help fix issues when they are found. It also has some issues occasionally but since it has only a ~3% usage these days you don't get as many complaints.
Blink is used by Chromium (which includes Edge, Chrome, Opera, Brave, and Samsung browsers). It has the biggest market share and probably the most people actively paid to work on it.
Webkit is currently only used by Safari and maintained by Apple alone. (Also all iOS browsers have to use webkit which is why iOS chrome has a lot of the same bugs as iOS safari etc). Apple has a conservative approach to Webkit and doesn't implement as many new features or standards as quickly as the other engines. It has the biggest non blink engine market share so it's usually the outlier when it comes to support issues.
Before 2013 Chromium was webkit based, but that year they made a fork and took their engine in a new direction so Webkit lost some of its previous maintainers.
Google could let Chrome rot: Microsoft let Internet Explorer rot back in the days before Edge (primarily because Microsoft recognised that browsers would compete with their Windows monopoly: which is exactly what happened).
