Can excess oil make french fries soggy?
Both. Is it soggy with moisture? Or is it soggy with oil?

In both cases, the problem isn't excess oil, after all, French Fries are usually deep fried. The problem is that the moisture isn't adequately driven out of the fry and/or that the fries sit in cold oil.

The crispiest French fries (read that non-soggy) are first soaked in cold water to remove excess starch, dried, deep fried in lower temperature oil to drive out all of the excess water, then deep fried in hotter oil to crisp the outside.

Then they are well drained while hot.

Unless the fries get quite crispy, they're going to get soggy with oil as the oil on the outside of the fries cool, even if there really isn't all that much oil clinging to the fry. Unless the moisture is well driven out (interior of the fry is fluffy), the fries will get soggy with moisture as they cool.

In the worst case scenario, you can have both greasy and wet cold fries.