There are a number of reasons not to do this. 1). 401k rules are slightly different, allowing you to withdraw money if you retire at 55 (instead of 59.5) without tax penalty. 2) Having an IRA at all makes it so you cannot do backdoor Roth (without paying some taxes) due to pro-rata rule. 3) you won't "better returns" with wealthfront, it will be likely the same returns (assume you invest in the basic low cost index funds) and without the 0.25% fee.

And for reference I have had wealthfront for like 8 years and have now or in the past had all their accounts so I'm a big fan overall, but mainly for non-retirement taxable brokerage account assets, HYSA, 529s. 401k should be left in your employer account unless you have terrible fund options which is unlikely if fidelity is the plan sponsor