So you made a claim that you cannot substantiate, and you're trying to shift the burden of proof to others (d!ck move).
I have not ever seen Canon announce that they lead the
full frame MILC market. Sony has stated that a couple of times. Sony used to say they led the mirrorless camera market...but Canon seems to have taken that spot away from them starting in 2022. So from that, it's evident that Sony lost MILC market share. Since for many years Sony was the only manufacturer selling FF MILCs, they had 100% of the market share and the only way to go from there is down. So the bottom line is that you can't back up your statement, and both current facts and logic refute your statement.
Incidentally, Canon was
#1 in full frame MILC sales last year in the US, which represents ~20% of global MILC sales.