OpenSSL was challenged by LibreSSL, and it didn't want to be replaced by it.
As for intention, it's difficult to know whether changing the API was for an improvement or to simply shut out a fundamentally improved LibreSSL from taking it over. It could be a little of both by different people of the OpenSSL project.
I get sick of the argument of, more eyes looking at a project. How many years did 1 feature of a dependency have to compile for 20 hours (by dependencies pulling in more sets of dependencies), when replacing that dependency with a FreeBSD one, allowed it to compile in seconds or minutes? People still don't understand this, when the fact is simply as it's explained. Now it can be audited easier. Something slim and designed well will be easier to audit. Bloated shit will have a lot of hidden problems, and it will remain hidden until it's organized according to function and performance. Not everything is bloated, some things are old, and additions got added on, that needed additional structure.
Python, for instance had to come out with a new version, because it has been added on to for functionality and features. It had to be organized and cleaned around its capabilities and expansions. I see Python as being efficient, despite that removing backwards compatibility was an inconvenience. For a project like Python, either maintaining backwards compatibility or removing backwards compatibility made sense. Hopefully there won't be a need for removing backwards compatibility in the future now, that it is designed for what it now needs. As for OpenSSL, I don't think it's all about making a better project, it's primarily about not fading away. More functionalities were needed, and it got expanded for those functions, then as it expands it gets less organized. It may have been too much to look at to find where to make improvements. Maybe it was too much code to maintain, that there wasn't enough incentive to accomplish a difficult task, then it got challenged.
Still, it's possible that LibreSSL may have lacked structure to replace everything that OpenSSL did. OpenSSL changing its structure for whatever motives there were was is in some way because of LibreSSL.
A problem is that programs that do the same thing often conflict with each other, because they install similar files in the same place. I wanted to use LibreSSL, but couldn't install everything I wanted to, when I tried it. So many programs depended on OpenSSL, too many programs had to be taken care of to do this.