Approaching a competitor of a company you were unsuccessful in buying

I recently lost out on a company I was bidding on in a competitive process. During due diligence, I discovered that I really liked the industry niche and would like to continue exploring it by doing a proprietary search and approach competitors in the space. I will destroy all material I gained through the due diligence process such as their financials etc, but there was obviously a lot of proprietary research that I did and documentation that I prepared in the process of bidding on the last firm that was informed by that target, is it ok to keep this material? is it ok to approach competitors knowing what I know about the target I missed out on? The NDA I signed asked for the destruction of material and to not disclose any of that information which I will do but I am still very well informed about its operations etc. in the absence of that material. I know that many investment firms concentrate on buying within industry niches and segments and therefore must amass a lot of confidential information on individual companies through that process but I just want to ensure that this is not an ethical violation of any kind beyond just the legal context.