I'm glad it does help.
I can not (and won't try to) explain what Erel had in his genius mind but : b4a 5 is a great step forward. In fact, I think we all had to think differently to adapt to its new functionalities.
The only thing I could say is : Erel probably had to (or wanted to) change some things because he had no better choice (think about the amount of energy and money Erel had to invest for that new release. If it was me, I would have been gone to the beach and never (oh never) had the spirit to recreate a new IDE from scratch. Even more because the previous one was already well working.
Another reason could be to be able to have one IDE for many platforms (but this is unsure and only a guess)