Yes, any high profile change on a movie this big is always going to generate a lot of press, a lot of theories, clickbait articles and unsubstantiated rumours. But the key point here is that the directors were outright fired after the majority of the work had theoretically already been done. On a project this expensive, that almost never happens and in this scenario Kathleen Kennedy is the veteran with a solid track record producing many many movies of this pedigree and the two directors are the relative rookies, I think it's obvious that whatever the whethertos and whyfors of what went on, it's the latter who were the problem.
I understand that Lord and Miller were fired because they were not capturing the style that Disney and Lucasfilm wanted. But why did Kathleen Kennedy wait so long to fire them, especially after they had directed a majority of the film? She didn't have the time to keep an eye on what was going on? Or use an assistant to keep an eye on the film? Why so long?