I also faced the same issue sp.js and sp.runtime.js etc. were not loading with page load I tried different approaches finally with below code I am able to load them, might help                                                                                                                                                                                

                                                                              
    <script type="text/javascript" src="/_layouts/15/sp.runtime.js"></script>
    <script type="text/javascript" src="/_layouts/15/sp.js"></script>
    <script type="text/javascript" src="/_layouts/15/sp.core.js"></script>
    <script type="text/javascript" src="/_layouts/15/1033/strings.js"></script>
    <script type="text/javascript" src="/_layouts/15/clienttemplates.js"></script>
    <script type="text/javascript" src="/_layouts/15/clientforms.js"></script>
    <script type="text/javascript" src="/_layouts/15/clientpeoplepicker.js"></script>
    <script type="text/javascript" src="/_layouts/15/autofill.js"></script>
    <script type="text/javascript">
    $(function() {
    	getSPOffset();
    	LoadData();
    });
    
    function initializePeoplePicker(peoplePickerElementId, allowMultipleValues, isPeopleOnly, GroupID, user) {
    //debugger;
    						SP.SOD.executeFunc("clienttemplates.js", "SPClientTemplates", function() {
    							var schema = {};
    						    if(isPeopleOnly) {
    						    	schema['PrincipalAccountType'] = 'User';
    						    }
    						    else {
    							    schema['PrincipalAccountType'] = 'User,DL,SecGroup,SPGroup';
    							}
    						    schema['SearchPrincipalSource'] = 15;
    						    schema['ResolvePrincipalSource'] = 15;
    						    schema['AllowMultipleValues'] = allowMultipleValues;
    						    schema['MaximumEntitySuggestions'] = 50;
    						    schema['Width'] = '280px';
    						    if(GroupID != null) {
    							    if (GroupID > 0) {  
    						            schema['SharePointGroupID'] = GroupID  
    						        }
    						    }
    						    SPClientPeoplePicker_InitStandaloneControlWrapper(peoplePickerElementId, user, schema);
    						});
    	
    }