Why Data Activator experience is removed from Microsoft fabric?

Data Activator and Reflex were renamed to Activator, and it is an item that is part of the Real-Time Intelligence workload (aka experience). All the features are intact, you just have to go somewhere else to create an Activator item. You can find it under "Track data" in the New item screen.

Microsoft recently retired the standalone Data Activator experience in Fabric.

Reason: Data Activator is being integrated into other Fabric experiences (especially Eventstream + Power BI alerts), so it’s no longer shown as a separate “experience tile.” The capability still exists but is being merged to provide a more unified real-time data activation workflow instead of a separate workspace.