The difference you are seeing is likely caused by a combination of effects from using different bodies and lenses. To compare lenses, use the same camera body. To compare camera bodies, use the same lens.
Canon and FujiFilm cameras do produce images with slightly different exposures at the same settings. According to the Wikipedia article on Film Speed, camera manufacturers can choose from "five different techniques for determining the exposure index rating at each sensitivity setting". FujiFilm is reported to use the SOS method. Canon apparently uses the REI method.
Here are some test images taken on Canon and FujiFilm bodies with the same lens and exposure settings. I estimate about a 2/3-stop difference.
Lenses can transmit different amounts of light, despite using the same aperture setting. Here are two images taken with different lenses using the same camera body and settings. Again, there is about a 2/3-stop difference.
I don't have the Canon body anymore, so cannot test using the brighter lens on Canon vs the darker one on FujiFilm. But I'd expect a 1.3-stop difference. To determine the specific contributions of various factors to the results you're seeing, you'll have to further test your equipment.
If it matters enough to you to do such testing, an EF-FX adapter will allow you to use Canon lenses on the FujiFilm body. You'll have to focus manually and use a hack to set the aperture. STM lenses and some USM lenses won't be able to focus. You could also use manual lenses with adapters for both EF and FX mounts. Options include Nikon F, Pentax K, and M42.
Differences in lighting. You took the test shot after noticing the ISO difference between the cameras. It's unlikely that lighting just happened to decrease every time you used the FujiFilm camera, but not the Canon camera.
Auto Lighting Optimizer (ALO). ALO works by reducing image contrast. A similar effect can be achieved on a FujiFilm X-Series camera by adjusting highlights and shadows settings. Your Canon test image does not look like an ALO-adjusted image. It does look like exposure was increased.