The period of inactivity is the most likely culprit. This just happened to mine as well, after several months of inactivity due to the pandemic. Albeit not as much, but I did have oil seeping out of the engine casing and oil filter and did get oil into the air filter. The oil seeping out of the engine casing and oil filter quickly stopped but I had to change the air filter and oil and oil filter to get all the issues resolved, including an intermittent check engine light that had popped up along with the oil.
Hope you get it all sorted out soon!
