Using 'capitalize upon' might imply exploitation or opportunism which isn't always viewed positively. He capitalized upon his friend's misfortune to take his position.
Pro Tip 2/3
Active Effort
The phrase suggests an active role in taking advantage of the situation. She quickly capitalized upon the new information to close the deal.
Pro Tip 3/3
Context Matters
Consider the conversational context since 'capitalize upon' can be too formal in casual settings. In the meeting, he wisely avoided saying he capitalized upon his colleague's error.