YouTube and Google while they’re virtually the same company, use a different algorithms - because they’re trying to accomplish different goals. YouTube is trying to keep users on their site while Google is trying to deliver the information you’re searching for.
Though Google owns YouTube, they are completely different platforms. YouTube is actually the third largest search engine on the web - but their SEO algorithm is not as advanced as Google’s because they haven’t spent the time, manpower, or money into backing it up. YouTube is king when looking at time on page, however - the content on YouTube can keep users entertained for hours.
Google in it’s itself has been building on top of the algorithm they have developed over and over again. So, understanding how all these things work can help you in building your strategy going forward.