Perhaps you did not apply the compression settings correctly. You may try to reduce resolution, modify compression ratio or downsample image. Please see the solutions below:
1. Select lower resolution under "General" label. The default 600 dpi might not be ideal. Windows Graphics Device Interface produces more image data with high resolution setting
2. Select JPEG: Reduce image size by lowering the quality
3. Select downsample and low resolution
You may use the ways above at the same time to reduce image size. It might take several tries to achieve the best result.