`data-` attributes removed from custom html code?

I just got started and am trying to embed an activity from Strava. I’ve successfully added their js library with the // src: technique. The rest of their embed code asks for html like:

<div class="strava-embed-placeholder" data-embed-type="activity" data-embed-id="10975141863" data-style="standard" data-from-embed="false"></div>

Which I can easily add in the post markdown. When I load the page the Strava embed renders but has no content. When looking at the source of the page it looks like the data- attributes have been removed. Which it looks like their JS library relies on to get the Strava activity ID so it can load the content.

<div class="strava-embed-placeholder"></div>

Is the parser sanitizing the output maybe? I would like to be able to embed my runs on my blog but I understand if that isn’t going to be possible.

Here is a link to Strava documentation for additional context.

Here is the actual page with the error: I did a run — James Christopher Hall

Thanks for any help!