Corustaria's marines all use rifles... And have proven themselves superb with them. Considering the conditions of their fighting, its not hard to believe some may have chosen to adapt them for standard line infantry usage.

Also, muskets are more inaccurate than bows at short range. But they have a longer range and better accuracy at range. Iirc, I was watching a programme on the history channel which said at 100m a Musket had a 7/10 chance of hitting the target in skilled hands (and still have considerable impact). At 200 it drops to 3/10. Meanwhile, hitting with a bow at ranges such as that and having enough force to hit the target (unless you are using a damn powerful bow) is pretty doubtful.

Arrows are effected a lot more by the wind and weather as well. In the rain, bows strings will become damp and useless, if a musket man could keep his powder dry he's good to go.

And the RoF of a bow is offset by the obvious need for more precise aiming.

In addition, if cavalry charges a bowman, he's pretty fucked even if he hhas a sword.
If cavalry charges a musketman, he likely has a bayonet attached (and even if he doesn't, he still has a better chance than a bowman) he'll perform better because he's essentially got a makeshift spear. Meanwhile, bowmen would either
Need to carry a spear with them
Be backed up by pikemen

Neither of which are ideal when you can just roll the two roles into one. Easier, more effective etc

In addition, musket balls have more force behind them on impact, thus more damae

Musket balls are also cheaper and easier to make than arrows, and easier for an army to carry

Finally, morale. I'd argue morale was hit harder when your friends were dropping around you to the sound of a loud crack.

Overall, muskets were just generally a more logical choice for an army