Again, it was answer to a hypothetical, one where it was stated that the tax rate goes to 70% or above.
As for soccer players, they also play where the money is. The average MLS salary was about $175 in 2018. The EPL was $3.2M. La Liga $1.6M. Manchester United had an average player salary of $7.6M.
Even with higher tax rates, they make more money. That is possible because MLS isn't really a thing in the US in comparison to European leagues. But, if the effective tax rates in Europe forced the comp levels below the effective levels of MLS, then you would see an influx of talent into the US which would improve the play and eventually increase the level of fan interest and franchise value and TV contracts which would, in theory, make the MLS even more attractive. Right now, it's not that way.
People go play where they can make the most money. That's the crux of the argument from the beginning.