Non-blanket L-1s are just really tough and probably the "best" example of irrational and unfair decision-making by USCIS. In short, extensive documentation of the structure/organization of the U.S. and foreign companies and of the employees managed and to be managed needs to be provided along with DETAILED descriptions of current and future managerial job duties. But L-1s are just tough and were tough even under the prior administration.
An L-1A - if you can show management of people now and in the U.S. - is much easier than an L-1B - unless the L-1B involves advanced scientific research and development.