Again, read the verse. It says ”And God is faithful; he will not let you be tempted beyond what you can bear. But when you are tempted, he will also provide a way out so that you can stand up under it.”
It says can, not will. There is a way of escape and they can take it. But not every believer successfully resists temptation. It looks like libertarian free will is the only explanation that can reconcile this passage with the facts. (Calvinists keep asking for a biblical text for LFW, I think I've got one). If Calvinism is true, then given God’s plan before the foundation of the world, Ted Haggard could not have avoided committing the sins he committed. There was no way of escape, and it was more than he could bear.
To unpack this a bit more, what does sufficient grace amount to? Remember, sufficient grace is resistible grace.
Such grace is sufficient inasmuch as you can resist temptation if you want to. As long as you want to resist temptation, you can.
Sufficient grace doesn’t mean you won’t wish to resist temptation. Just that if you want to, you’ll be able to overcome the temptation.
But isn’t that utterly vacuous? Why do sinners, Christian or otherwise, give into temptation in the first place?
Because they want to. They want to go all the way. Because the temptation to sin is more tempting than the urge (if there is any) to resist.
Even if there’s a part of them that doesn’t want to, that hates doing it, or hates the foreseeable consequences, that is overpowered by a stronger desire.
So isn’t sufficient grace otiose? It’s a conditional grace. If you want to resist, you can–but that doesn’t stop you from wanting to succumb. From wanting it so badly that you do succumb. So what difference does it make?