100% agree with you. Median salary is $800k, which is amazing, but if you only get 2-3 years out of it, need to index the take-home and live like a college student to make it worth anything after compounding.
Then the expenses related to their jobs - food, training, etc. Shit ain't cheap. And before you ask - no, not all NFL teams really provide a ton to their players. My local team, Miami, has the best nutrition and food staff in the league. Players love it. Other teams don't provide much besides Gatorade on game days or other shitty protein snacks provided by league sponsors. Forget about full nutritious meals. Then you've got some teams with a great strength and conditioning staff. Other teams simply don't, which leaves players to find their own private solutions. This all adds up.
Many (but not all) states have tax credit arangements with other states so you wouldn't pay full tax on all income to your state of residence as well as the taxes owed to the states you worked in.