Gibbs for Derrick Henry and Matthew Stafford, is that clear-cut collusion?

More context:

I let the league vote on it and it didn’t get rejected. Some of my league mates are still giving me a hard time about it after several weeks.

The person giving Gibbs away was out of playoff contention several weeks ago. The person getting Gibbs already has a very scary team.
The trade is between father and son. There is money on the table and several coworkers in the league that are not super familiar with fantasy football in the first place.

Should I have not allowed this to go through or is there enough leeway there to be reasonable?