Presumably you're conveying the results of your research, which means new facts are on the table that the "mismanagers" weren't previously aware of. They assigned you that research work presumably because they wanted to know those facts. Now that you're showing up with useful information, they can go back and deliver an even better estimate of the project than they had before.

If you show up and are like "hey idiots, you fucked up the estimate, man you're dumb" then, sure, people will react negatively. If you show up and say "you were right that we needed to look into this more; we found 9 months of work we hadn't incorporated into the plan" then they're going to have a lot of work to do, but they probably aren't going to be unhappy about being in a position of higher certainty.

To some extent, it's not really different from what engineers do. Are you mad when there's a production outage? No. You just debug it and mitigate it. Project planning is no different; new facts are on the table, and the plan has to change. Changing the plan is a lot of work, and that's why project management is a dedicated profession. They can now go do their job better with the data that you collected. No reason to be mad.