It's a bit misleading to say that; you're not accounting for population growth, for one thing. According to https://www-fars.nhtsa.dot.gov/states/statespedestrians.aspx, the numbers are:
year killed population fatality rate (per 100,000 people)
2010 4,302 309,322,000 1.39
2019 6,205 328,240,000 1.89
So fatality rate did increase, but not by 50%. And in fact, it's down to 1.89 in 2019 from 1.95 in 2018, to give some context as to wiggle room. Also, the rate varies wildly by state (anywhere from 0.48 to 3.96)